(colloquial, humorous) What's up?

Alternative form of what's up Doc

(dated) Synonym of know what is what

(idiomatic) Used to express disappointment about someone's uncharacteristic or abnormal past actions.

(dated) Synonym of know what is what

(dated) whatchamacallit

(rare) Alternative form of whatsoever

(informal) Synonym of what's your poison

Alternative form of whatsitsname.

(emphatic) Used to express that the thing in question is an ideal example.