(UK, dated) Used to add emphasis to, and to seek agreement with, a previous statement.

Alternative form of what's what

(idiomatic) Precisely what the situation really is or what the facts truly are; the true state of things.

(euphemistic, African-American Vernacular) What the hell.

(Manglish, Singlish) Emphasizes the truth of an assertion made to contradict an evidently false assumption held by the listener.

(interrogative) Which thing, event, circumstance, etc.: used in asking for the specification of an identity, quantity, quality, etc. / (fused relative) That which; those that; the thing(s) that.

(obsolete, uncountable) Something; thing; stuff. / (countable) The identity of a thing, as an answer to a question of what.

An expression of surprise or disbelief. / What do you want? An abrupt, usually unfriendly enquiry as to what a person desires.

(interrogative) Which, especially which of an open-ended set of possibilities. / (relative) Which; the ... that. / (relative) Any ... that; all ... that; whatever.

(interrogative) In what way; to what extent.