leastadjective, pronoun, adverb1the smallest amount of something: Sue has a lot of money, Jane has less, and Kate has the least.oppositemost2less than all others: I bought the least expensive tickets.oppositemostat least1not less than: It will cost at least €150.2although other things are bad: We're not rich, but at least we're happy.not in the leastnot at all: ‘Are you angry?’ ‘Not in the least!’