mountain trail vs trail

mountain trail and trail both are nouns.

Word	Noun	Adjective	Verb	Adverb
mountain trail	Yes	No	No	No
trail	Yes	No	Yes	No

As nouns, trail is a hypernym of mountain trail; that is, trail is a word with a broader meaning than mountain trail:

mountain trail (noun)	trail (noun)
a trail through mountainous country	a path or track roughly blazed through wild or hilly country
	evidence pointing to a possible solution
	a track or mark left by something that has passed

mountain trail (verb)	trail (verb)
	drag loosely along a surface; allow to sweep the ground
	hang down so as to drag along the ground
	go after with the intent to catch
	move, proceed, or walk draggingly or slowly
	to lag or linger behind