shorten vs trim down

shorten and trim down both are verbs.

Word	Noun	Adjective	Verb	Adverb
shorten	No	No	Yes	No
trim down	No	No	Yes	No

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

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

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

shorten (verb)	trim down (verb)
become short or shorter	cut down on; make a reduction in
make shorter than originally intended; reduce or retrench in length or duration
reduce in scope while retaining essential elements
edit by omitting or modifying parts considered indelicate
make short or shorter