think over vs puzzle

think over is not a noun while puzzle is a noun.

Word	Noun	Adjective	Verb	Adverb
think over	No	No	Yes	No
puzzle	Yes	No	Yes	No

As verbs, puzzle is a hyponym of think over; that is, puzzle is a word with a more specific, narrower meaning than think over:

think over: reflect deeply on a subject
puzzle: be uncertain about; think about without fully understanding or being able to decide

Other hyponyms of think over include premeditate, theologise, theologize, introspect, bethink, cogitate, question, wonder, consider, study.

think over (noun)	puzzle (noun)
	a game that tests your ingenuity
	a particularly baffling problem that is said to have a correct solution

think over (verb)	puzzle (verb)
reflect deeply on a subject	be a mystery or bewildering to
	be uncertain about; think about without fully understanding or being able to decide