someone who makes an offer
"When the auctioneer called out the final price, the highest bidder won the antique vase."
someone who makes a bid at cards
"During the intense final hand, the bidder raised his voice to signal that he was all in on the last card."
Someone who bids (all senses), but most commonly, one offers to pay a specified price at an auction
"The highest bidder walked away with the vintage watch after outbidding all other competitors."
In plain English: A bidder is someone who makes an offer to buy something during an auction.
"The highest bidder won the auction for the vintage car."
Usage: A bidder is someone who makes an offer to purchase an item at an auction or tender. Use this term specifically when referring to participants actively competing to pay a set price for goods or services.
A surname.
"The local auction house announced that Mr. Bidder had been selected as the new chairman of the board."
The word bidder comes from Middle English and originally meant a person who makes an offer or proposal. It entered modern usage by simply adding the suffix "-er" to the verb "bid.