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