slowdown vs holdup

slowdown and holdup both are nouns.

Word	Noun	Adjective	Verb	Adverb
slowdown	Yes	No	No	No
holdup	Yes	No	No	No

As nouns, holdup is a hypernym of slowdown; that is, holdup is a word with a broader meaning than slowdown:

slowdown: the act of slowing down or falling behind
holdup: the act of delaying; inactivity resulting in something being put off until a later time

Other hypernyms of slowdown include delay.

slowdown (noun)	holdup (noun)
the act of slowing down or falling behind	robbery at gunpoint
	the act of delaying; inactivity resulting in something being put off until a later time