step on it vs scud

step on it is not a noun while scud is a noun.

Word	Noun	Adjective	Verb	Adverb
step on it	No	No	Yes	No
scud	Yes	No	Yes	No

As verbs, scud is a hyponym of step on it; that is, scud is a word with a more specific, narrower meaning than step on it:

Other hyponyms of step on it include barge, push forward, thrust ahead, buck, charge, shoot, shoot down, tear, dart, dash, flash, scoot, shoot.

step on it (noun)	scud (noun)
	the act of moving along swiftly (as before a gale)

step on it (verb)	scud (verb)
move hurridly	run or move very quickly or hastily
	run before a gale