on the spur of the moment vs abruptly

on the spur of the moment and abruptly both are adverbs.

Word	Noun	Adjective	Verb	Adverb
on the spur of the moment	No	No	No	Yes
abruptly	No	No	No	Yes

As adverbs, on the spur of the moment and abruptly are synonyms defined as:

on the spur of the moment and abruptly: quickly and without warning
on the spur of the moment and abruptly: happening unexpectedly
on the spur of the moment and abruptly: on impulse; without premeditation

Other synonyms of on the spur of the moment include all of a sudden, dead, of a sudden, short, suddenly.

on the spur of the moment (adverb)	abruptly (adverb)
quickly and without warning; happening unexpectedly; on impulse; without premeditation	quickly and without warning; happening unexpectedly; on impulse; without premeditation