underprice vs sell

underprice is not a noun while sell is a noun.

Word	Noun	Adjective	Verb	Adverb
underprice	No	No	Yes	No
sell	Yes	No	Yes	No

As verbs, sell is a hypernym of underprice; that is, sell is a word with a broader meaning than underprice:

underprice (noun)	sell (noun)
	the activity of persuading someone to buy

underprice (verb)	sell (verb)
sell at artificially low prices	persuade somebody to accept something
	exchange or deliver for money or its equivalent
	do business; offer for sale as for one's livelihood
	give up for a price or reward
	deliver to an enemy by treachery
	be sold at a certain price or in a certain way
	be responsible for the sale of
	be approved of or gain acceptance