greenhead \ˈ ̷ ̷ˌ ̷ ̷\noun 1.archaic: greenhorn 2. a.: mallard b.: greater scaup 3.alsogreenhead fly: any of several green-eyed biting flies of the family Tabanidae; especially: a large fly (Tabanus nigrovittatus) common near salt marshes 4.: striped bass