switchblade knife vs switchblade

switchblade knife and switchblade both are nouns.

Word	Noun	Adjective	Verb	Adverb
switchblade knife	Yes	No	No	No
switchblade	Yes	No	No	No

As nouns, switchblade knife and switchblade are synonyms defined as:

switchblade knife and switchblade: a pocketknife with a blade that springs open at the press of a button

Other synonyms of switchblade knife include flick-knife, flick knife.

switchblade knife (noun)	switchblade (noun)
a pocketknife with a blade that springs open at the press of a button	a pocketknife with a blade that springs open at the press of a button