impulsive vs madcap

impulsive is not a noun while madcap is a noun.

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

As adjectives, impulsive and madcap are synonyms defined as:

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

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

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

impulsive (adjective)	madcap (adjective)
determined by chance or impulse or whim rather than by necessity or reason	characterized by undue haste and lack of thought or deliberation
having the power of driving or impelling
characterized by undue haste and lack of thought or deliberation
proceeding from natural feeling or impulse without external stimulus
without forethought