Hysterically is an adverb - Word Type.
Is hysterically an adverb?
hysterically adverb - Definition, pictures, pronunciation and usage notes | Oxford Advanced Learner's Dictionary at OxfordLearnersDictionaries.com.
Is hysterically an adjective?
uncontrollably emotional. irrational from fear, emotion, or an emotional shock. causing unrestrained laughter; very funny: Oh, that joke is hysterical!