sell vs auction off

sell is a noun but auction off is not a noun.

Word	Noun	Adjective	Verb	Adverb
sell	Yes	No	Yes	No
auction off	No	No	Yes	No

As verbs, auction off is a hyponym of sell; that is, auction off is a word with a more specific, narrower meaning than sell:

sell (noun)	auction off (noun)
the activity of persuading someone to buy

sell (verb)	auction off (verb)
persuade somebody to accept something	sell at an auction
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