subtract vs trim back

subtract and trim back both are verbs.

Word	Noun	Adjective	Verb	Adverb
subtract	No	No	Yes	No
trim back	No	No	Yes	No

As verbs, trim back is a hypernym of subtract; that is, trim back is a word with a broader meaning than subtract:

Other hypernyms of subtract include bring down, cut, cut back, cut down, reduce, trim, trim down.

subtract (verb)	trim back (verb)
take off or away	cut down on; make a reduction in
make a subtraction