rethink vs flip-flop

rethink and flip-flop both are nouns.

Word	Noun	Adjective	Verb	Adverb
rethink	Yes	No	Yes	No
flip-flop	Yes	No	Yes	No

As nouns, flip-flop is a hypernym of rethink; that is, flip-flop is a word with a broader meaning than rethink:

Other hypernyms of rethink include change of mind, reversal, turnabout, turnaround.

rethink (noun)	flip-flop (noun)
thinking again about a choice previously made	a backward somersault
	an electronic circuit that can assume either of two stable states
	a backless sandal held to the foot by a thong between the big toe and the second toe
	a decision to reverse an earlier decision

rethink (verb)	flip-flop (verb)
change one's mind	reverse (a direction, attitude, or course of action)