(colloquial) Who says so; on whose authority?

(slang) say what.

(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

Alternative form of suffice it to say

An introduction to a statement that will be brief, indicating that further discussion would be futile, too lengthy, too private, etc.

Sadly; unfortunately.

(idiomatic) It is my estimate or opinion.

Apparently, according to others.

Alternative form of so to speak