Least \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.

Source: Webster's Revised Unabridged Dictionary (1913)