brainish vs madcap

brainish is not a noun while madcap is a noun.

Word	Noun	Adjective	Verb	Adverb
brainish	No	Yes	No	No
madcap	Yes	Yes	No	No

As adjectives, brainish and madcap are synonyms defined as:

brainish and madcap: characterized by undue haste and lack of thought or deliberation

Other synonyms of brainish include hotheaded, impetuous, impulsive, tearaway.

brainish (noun)	madcap (noun)
	a reckless impetuous irresponsible person

brainish (adjective)	madcap (adjective)
characterized by undue haste and lack of thought or deliberation	characterized by undue haste and lack of thought or deliberation