(colloquial) I say so; on my authority.

(slang) say what.

(colloquial) Who says so; on whose authority?

(Britain, dated) An exclamation of surprise or protest. / Used for emphasis, or when resuming after diversion or interruption.

(idiomatic, colloquial) Used to indicate emphatic agreement

Sadly; unfortunately.

(idiomatic) It is my estimate or opinion.

(Ireland, UK, historical) A unionist mass protest campaign against the provisions of the 1985 Anglo-Irish Agreement which gave the government of the Republic of Ireland an advisory role in Northern Ireland's government.

(idiomatic) To express the essential characteristics of a person, thing, or situation in a concise, well-crafted turn of phrase or in some other pithy manner.

Third-person singular simple present indicative form of say it all