-sto·mum \ˈstōməm, in sense 2 _stəməm\noun combining form (plural-sto·ma \-mə\) Etymology: New Latin, from Greek stoma mouth — more at stomach 1.: mouth : opening : stoma < prestomum > 2.: creature with (such) a mouth — in generic names < Amphistomum > < Oesophagostomum >