hysterical
adj.adj. extremely funny or impossible to stop laughing at. It can also describe someone who is so upset or excited that they have lost control of their emotions.
adj. characterised by uncontrolled extreme emotion or, in a common informal sense, extremely humorous. Often used predicatively after linking verbs like 'become' or 'be'.
That comedy show was absolutely hysterical.
The audience was hysterical with laughter after the comedian's final joke about his cat.
The witness became hysterical during the cross-examination, sobbing so uncontrollably that the judge had to call for a brief recess to allow her to regain her composure.
From hysteric + -al, from Latin hystericus, from Ancient Greek ὑστερικός (husterikós, “suffering in the womb, hysterical”), from ῠ̔στέρᾱ (hŭstérā, “womb”).
Often modified by 'absolutely' or 'completely'. When meaning 'funny', it is informal; when meaning 'uncontrolled emotion', it is more formal or medical.