slow up vs decelerate

slow up and decelerate both are verbs.

Word	Noun	Adjective	Verb	Adverb
slow up	No	No	Yes	No
decelerate	No	No	Yes	No

As verbs, slow up and decelerate are synonyms defined as:

Other synonyms of slow up include retard, slow, slow down.

As verbs, decelerate is a hypernym of slow up; that is, decelerate is a word with a broader meaning than slow up:

Other hypernyms of slow up include retard, slow, slow down, slow up.

slow up (verb)	decelerate (verb)
lose velocity; move more slowly	lose velocity; move more slowly
cause to proceed more slowly	reduce the speed of
become slow or slower