bidding vs overcall

bidding and overcall both are nouns.

Word	Noun	Adjective	Verb	Adverb
bidding	Yes	No	No	No
overcall	Yes	No	No	No

As nouns, overcall is a hyponym of bidding; that is, overcall is a word with a more specific, narrower meaning than bidding:

bidding: (bridge) the number of tricks a bridge player is willing to contract to make
overcall: (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)

Other hyponyms of bidding include contract, declaration, takeout, overbid, pre-empt, preempt, preemptive bid.

bidding (noun)	overcall (noun)
a request to be present	(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)
(bridge) the number of tricks a bridge player is willing to contract to make
an authoritative direction or instruction to do something