1. any uncultivated species of Avena, esp. a common weedy grass, A. fatua, resembling the cultivated oat.
2. a hardy plant, Uvularia sessilifolia, of the lily family, of eastern North America, having deep green, hairy leaves and greenish-yellow, tubular flowers.
3. sow one's wild oats, to have a youthful fling at reckless and indiscreet behavior, esp. to be promiscuous before marriage.