English Alternative forms sea-swine, sea swine Etymology From sea + swine. Compare Middle English brunswin (“porpoise”). Noun seaswine pl (plural only) Porpoises. 1828, John Davidson Godman, American natural history:The seaswine are almost always seen in troops, especially in their sexual season, which is in the month of August. Wikiwand - on Seamless Wikipedia browsing. On steroids.