Entry 1 sense Webster, 1913 Avena /äv-ān'-ə/ · A·ve·na · IPA /ɑvˈeɪnə/ 01 n. A genus of grasses, including the common oat (Avena sativa); the oat grasses. 1. A genus of grasses, including the common oat (Avena sativa); the oat grasses.(Bot.)