1. [n]  any stratum lying underneath another
2. [n]  the substance acted upon by an enzyme or ferment

1. \Sub"strate\, n.
   A substratum. [R.]
   

2. \Sub"strate\, a.
   Having very slight furrows. [R.]
   

3. \Sub*strate"\, v. t. [L. substratus, p. p. of
   substrahere. See {Substratum}.]
   To strew or lay under anything. [Obs.]
         The melted glass being supported by the substrated
         sand.                                    --Boyle.
   

The body or base layer of an integrated circuit, onto which other layers are deposited to form the circuit. The substrate is usually Silicon, though Sapphire is used for certain applications, particularly military, where radiation resistance is important. The substrate is originally part of the wafer from which the die is cut. It is used as the electrical ground for the circuit.

1. 1. The specific molecule an enzyme acts upon.
   2. A stationary surface upon which other things can attach. For example: cells in culture on a plastic or glass substrate, invertebrate larvae settling on a patch of bare rock (a hard substrate), or worms burrowing into mud or other sediment (a soft substrate).
2. Mineral or organic material that forms the bed of a stream.