back up vs gum up

back up and gum up both are verbs.

Word	Noun	Adjective	Verb	Adverb
back up	No	No	Yes	No
gum up	No	No	Yes	No

As verbs, gum up is a hyponym of back up; that is, gum up is a word with a more specific, narrower meaning than back up:

Other hyponyms of back up include block, choke up, lug, stuff, silt, silt up.

back up (verb)	gum up (verb)
establish as valid or genuine	stick together as if with gum
become or cause to become obstructed
make a copy of (a computer file) especially for storage in another place as a security copy
move backwards from a certain position
give moral or psychological support, aid, or courage to