flick knife vs pocket knife

flick knife and pocket knife both are nouns.

Word	Noun	Adjective	Verb	Adverb
flick knife	Yes	No	No	No
pocket knife	Yes	No	No	No

As nouns, pocket knife is a hypernym of flick knife; that is, pocket knife is a word with a broader meaning than flick knife:

flick knife: a pocketknife with a blade that springs open at the press of a button
pocket knife: a knife with a blade that folds into the handle; suitable for carrying in the pocket

Other hypernyms of flick knife include pocketknife.

flick knife (noun)	pocket knife (noun)
a pocketknife with a blade that springs open at the press of a button	a knife with a blade that folds into the handle; suitable for carrying in the pocket