adj. Lowest in importance or rank.adj. Smallest in magnitude or degree.adj. Slightest or tiniest: didn't care the least bit. ad. To or in the lowest or smallest degree.n. One that is the lowest or smallest in importance, rank, magnitude, or degree: The dinner menu is the least of my worries tonight. The least you can do is to be polite. idiom. at least According to the lowest possible assessment; not less than: waited at least an hour. idiom. at least In any event; anyway: You might at least answer. idiom. in the least At all: I don't mind in the least. idiom. least of all Particularly not: Nobody cared, least of all the manager.