spice up vs pepper

spice up is not a noun while pepper is a noun.

Word	Noun	Adjective	Verb	Adverb
spice up	No	No	Yes	No
pepper	Yes	No	Yes	No

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

Other hyponyms of spice up include ginger.

spice up (noun)	pepper (noun)
	pungent seasoning from the berry of the common pepper plant of East India; use whole or ground
	sweet and hot varieties of fruits of plants of the genus Capsicum
	any of various tropical plants of the genus Capsicum bearing peppers
	climber having dark red berries (peppercorns) when fully ripe; southern India and Sri Lanka; naturalized in northern Burma and Assam

spice up (verb)	pepper (verb)
make more interesting or flavorful	attack and bombard with or as if with missiles
add herbs or spices to	add pepper to