a. [ OE. last, lest, AS. l&aemacr_;sast, l&aemacr_;sest, superl. of l&aemacr_;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. [ 1913 Webster ]

☞ Least is often used with the, as if a noun. [ 1913 Webster ]

I am the least of the apostles. 1 Cor. xv. 9. [ 1913 Webster ]

At least, or
At the least, at the least estimate, consideration, chance, etc.; being no less than; hence, at any rate; at all events; even. See However. [ 1913 Webster ]

He who tempts, though in vain, at least asperses
The tempted with dishonor. Milton. [ 1913 Webster ]

Upon the mast they saw a young man, at least if he were a man, who sat as on horseback. Sir P. Sidney.

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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. 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. [ 1913 Webster ]

adv. In the smallest or lowest degree; in a degree below all others; as, to reward those who least deserve it. [ 1913 Webster ]

conj. See Lest, conj. [ Obs. ] Spenser. [ 1913 Webster ]

{ } adv. At least; at all events. [ Colloq. ] [ 1913 Webster ]

At leastways, or
At leastwise, at least. [ Obs. ] Fuller. [ 1913 Webster ]