overbid vs underbid

overbid is a noun but underbid is not a noun.

Word	Noun	Adjective	Verb	Adverb
overbid	Yes	No	Yes	No
underbid	No	No	Yes	No

overbid (noun)	underbid (noun)
a bid that is higher than preceding bids
(bridge) a bid that is higher than your opponent's bid (especially when your partner has not bid at all and your bid exceeds the value of your hand)

overbid (verb)	underbid (verb)
bid more than the object is worth	bid too low
to bid for more tricks than one can expect to win	bid lower than a competing bidder
	bid (a hand of cards) at less than the strength of the hand warrants