\Least\, a. [OE. last, lest, AS. l?sast, l?sest, superl.
of l?ssa less. See {Less}, a.] [Used as the superlative of
little.]
Smallest, either in size or degree; shortest; lowest; most
unimportant; as, the least insect; the least mercy; the least
space.
Note: Least is often used with the, as if a noun.
            I am the least of the apostles.    --1 Cor. xv.
                                               9.
{At least}, or {At the least}, at the least estimate,
   consideration, chance, etc.; hence, at any rate; at all
   events; even. See {However}.
         He who tempts, though in vain, at least asperses The
         tempted with dishonor.                --Milton.
         Upon the mast they saw a young man, at least if he
         were a man, who sat as on horseback.  --Sir P.
                                               Sidney.
{In least}, or {In the least}, in the least degree, manner,
   etc. ``He that is unjust in the least is unjust also in
   much.'' --Luke xvi. 10.
{Least squares} (Math.), a method of deducing from a number
   of carefully made yet slightly discordant observations of
   a phenomenon the most probable values of the unknown
   quantities.
Note: It takes as its fundamental principle that the most
      probable values are those which make the sum of the
      squares of the residual errors of the observation a
      minimum.

\Least\, adv.
In the smallest or lowest degree; in a degree below all
others; as, to reward those who least deserve it.

\Least\, conj.
See {Lest}, conj. [Obs.] --Spenser.