(colloquial) A silly person. / (endearing, gently derogatory) A term of address. / (colloquial) A mistake.

(now regional or colloquial) Sillily: in a silly manner.

Laughable or amusing through foolishness or a foolish appearance. / (of numbers, particularly prices) Absurdly large. / Good; pious. / Holy.

plural of silliness

(uncountable) That which is perceived as silly or frivolous. / (countable) An act that is silly; a result of being silly.

plural of silly / (informal, as "the sillies") A period of foolish behaviour.

plural of silly pill

(humorous) A hypothetical pill that makes those who take it silly.

(now rare, dialectal) The caul which sometimes envelopes the top of a child's head after birth.

(idiomatic, journalism) A period, usually during the summertime, when news media tend to place increased emphasis on reporting light-hearted, offbeat, or bizarre stories.