trail vs drop back

trail is a noun but drop back is not a noun.

Word	Noun	Adjective	Verb	Adverb
trail	Yes	No	Yes	No
drop back	No	No	Yes	No

As verbs, trail and drop back are synonyms defined as:

Other synonyms of trail include drag, drop behind, get behind, hang back.

trail (noun)	drop back (noun)
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

trail (verb)	drop back (verb)
drag loosely along a surface; allow to sweep the ground	take position in the rear, as in a military formation or in the line of scrimmage in football
hang down so as to drag along the ground	to lag or linger behind
go after with the intent to catch
move, proceed, or walk draggingly or slowly
to lag or linger behind