(philosophy) Essence; quiddity. / Quality; quantity.

plural of whatness

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

Alternative form of what's what

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

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

(by ellipsis) Used to express astonishment or incredulity, as a question or questioning of the situation at hand, without requiring any specific vulgarity as intensifier.

(slang, African-American Vernacular) A casual greeting.

(idiomatic, dated) Something of the kind, whatever (used to terminate a vague list).

Alternative spelling of whatnot