From Longman Business Dictionary
auctioneerauc·tio·neer /ˌɔːkʃəˈnɪəˌɒːkʃəˈnɪr/ noun [countableC]JOBCOMMERCE someone who is in charge of selling goods at an auctionEach bid is a separate offer and a contract is not made until the auctioneer accepts one of them.