retrench vs cut back

retrench and cut back both are verbs.

Word	Noun	Adjective	Verb	Adverb
retrench	No	No	Yes	No
cut back	No	No	Yes	No

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

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

retrench (verb)	cut back (verb)
make a reduction, as in one's workforce	place restrictions on
tighten one's belt; use resources carefully	cut down on; make a reduction in
	cultivate, tend, and cut back the growth of
	return in time