1. [n]  a cashbox with an adding machine to register transactions; used in shops to add up the bill
2. [n]  a regulator (as a sliding plate) for regulating the flow of air into a furnace or other heating device
3. [n]  an air passage (usually in the floor or a wall of a room) for admitting or excluding heated air from the room
4. [n]  (computer science) memory device that is the part of computer memory that has a specific address and that is used to hold information of a specific kind
5. [n]  the timbre characteristic of a certain range and manner of production of the human voice
6. [n]  an official written record of names or events or transactions
7. [n]  a book in which names and transactions are listed
8. [v]  register in a public office or in a court of law; "file for divorce"; "file a complaint"
9. [v]  enter into someone's consciousness; "Did this event register in your parents' minds?"
10. [v]  indicate a certain reading; of gauges and instruments; "The thermometer showed thirteen degrees below zero"; "The gauge read `empty'"
11. [v]  send by registered mail; "I'd like to register this letter"
12. [v]  register to vote; "register for an election"
13. [v]  manipulate the registers of an organ
14. [v]  be aware of; "Did you register any change when I pressed the button?"
15. [v]  show in one's face; "Her surprise did not register"
16. [v]  record in writing; enter into a register
17. [v]  register as a candidate for several parties

1. \Reg"is*ter\, v. t. (Securities)
   To enter the name of the owner of (a share of stock, a bond,
   or other security) in a register, or record book. A
   registered security is transferable only on the written
   assignment of the owner of record and on surrender of his
   bond, stock certificate, or the like.
   

2. \Reg"is*ter\ (r[e^]j"[i^]s*t[~e]r), n. [OE. registre,
   F. registre, LL. registrum,regestum, L. regesta, pl., fr.
   regerere, regestum, to carry back, to register; pref. re- re-
   + gerere to carry. See {Jest}, and cf. {Regest}.]
   1. A written account or entry; an official or formal
      enumeration, description, or record; a memorial record; a
      list or roll; a schedule.
            As you have one eye upon my follies, . . . turn
            another into the register of your own. --Shak.
   2. (Com.)
      (a) A record containing a list and description of the
          merchant vessels belonging to a port or customs
          district.
      (b) A certificate issued by the collector of customs of a
          port or district to the owner of a vessel, containing
          the description of a vessel, its name, ownership, and
          other material facts. It is kept on board the vessel,
          to be used as an evidence of nationality or as a
          muniment of title.
   3. [Cf. LL. registrarius. Cf. {Regisrar}.] One who registers
      or records; a registrar; a recorder; especially, a public
      officer charged with the duty of recording certain
      transactions or events; as, a register of deeds.
   4. That which registers or records. Specifically:
      (a) (Mech.) A contrivance for automatically noting the
          performance of a machine or the rapidity of a process.
      (b) (Teleg.) The part of a telegraphic apparatus which
          records automatically the message received.
      (c) A machine for registering automatically the number of
          persons passing through a gateway, fares taken, etc.;
          a telltale.
   5. A lid, stopper, or sliding plate, in a furnace, stove,
      etc., for regulating the admission of air to the fuel;
      also, an arrangement containing dampers or shutters, as in
      the floor or wall of a room or passage, or in a chimney,
      for admitting or excluding heated air, or for regulating
      ventilation.
   6. (Print.)
      (a) The inner part of the mold in which types are cast.
      (b) The correspondence of pages, columns, or lines on the
          opposite or reverse sides of the sheet.
      (c) The correspondence or adjustment of the several
          impressions in a design which is printed in parts, as
          in chromolithographic printing, or in the manufacture
          of paper hangings. See {Register}, v. i. 2.
   7. (Mus.)
      (a) The compass of a voice or instrument; a specified
          portion of the compass of a voice, or a series of
          vocal tones of a given compass; as, the upper, middle,
          or lower register; the soprano register; the tenor
          register.
   Note: In respect to the vocal tones, the thick register
         properly extends below from the F on the lower space of
         the treble staff. The thin register extends an octave
         above this. The small register is above the thin. The
         voice in the thick register is called the chest voice;
         in the thin, the head voice. Falsetto is a kind off
         voice, of a thin, shrull quality, made by using the
         mechanism of the upper thin register for tones below
         the proper limit on the scale. --E. Behnke.
      (b) A stop or set of pipes in an organ.
   {Parish register}, A book in which are recorded the births,
      baptisms, marriages, deaths, and burials in a parish.
   Syn: List; catalogue; roll; record; archives; chronicle;
        annals. See {List}.
   

3. \Reg"is*ter\ (r[e^]j"[i^]s*t[~e]r), v. t. [imp. & p. p.
   {Registered} (-t[~e]rd); p. pr. & vb. n. {Registering}.] [Cf.
   F. regisrer, exregistrer, LL. registrare. See {Register}, n.]
   1. To enter in a register; to record formally and distinctly,
      as for future use or service.
   2. To enroll; to enter in a list.
            Such follow him as shall be registered. --Milton.
   {Registered letter}, a letter, the address of which is, on
      payment of a special fee, registered in the post office
      and the transmission and delivery of which are attended to
      with particular care.
   

4. \Reg"is*ter\, v. i.
   1. To enroll one's name in a register.
   2. (Print.) To correspond in relative position; as, two
      pages, columns, etc., register when the corresponding
      parts fall in the same line, or when line falls exactly
      upon line in reverse pages, or (as in chromatic printing)
      where the various colors of the design are printed
      consecutively, and perfect adjustment of parts is
      necessary.
   

1. One of a small number of high-speed memory locations in a computer's CPU. Registers differ from ordinary random access memory in several respects:

There are only a small number of registers (the "register set"), typically 32 in a modern processor though some, e.g. SPARC, have as many as 144. A register may be directly addressed with a few bits. In contrast, there are usually millions of words of main memory (RAM), requiring at least twenty bits to specify a memory location. Main memory locations are often specified indirectly, using an indirect addressing mode where the actual memory address is held in a register.

Registers are fast; typically, two registers can be read and a third written -- all in a single cycle. Memory is slower; a single access can require several cycles.

The limited size and high speed of the register set makes it one of the critical resources in most computer architectures. Register allocation, typically one phase of the back-end, controls the use of registers by a compiled program.

See also accumulator, FUBAR, orthogonal, register dancing, register allocation, register spilling.

2. An addressable location in a memory-mapped peripheral device. E.g. the transmit data register in a UART.