like crazy vs like mad

like crazy and like mad both are adverbs.

Word	Noun	Adjective	Verb	Adverb
like crazy	No	No	No	Yes
like mad	No	No	No	Yes

As adverbs, like crazy and like mad are synonyms defined as:

like crazy and like mad: (informal) with great speed or effort or intensity; used for emphasis

Other synonyms of like crazy include like hell, like sin, like the devil, like thunder.

like crazy (adverb)	like mad (adverb)
(informal) with great speed or effort or intensity; used for emphasis	(informal) with great speed or effort or intensity; used for emphasis