shorten vs cut back

shorten and cut back both are verbs.

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

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

shorten: make shorter than originally intended; reduce or retrench in length or duration
cut back: cut down on; make a reduction in

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

shorten (verb)	cut back (verb)
become short or shorter	place restrictions on
make shorter than originally intended; reduce or retrench in length or duration	cut down on; make a reduction in
reduce in scope while retaining essential elements	cultivate, tend, and cut back the growth of
edit by omitting or modifying parts considered indelicate	return in time
make short or shorter