the world > physical sensation > sexual relations > sexual activity > [adjective] > of penis, clitoris, or nipples: erect (3)
Of the penis, clitoris, or nipples: erect. In later use also of a man: having an erect penis. Cf. sense B. 9 and hard-on, adj. n.
Of the penis, nipples, or clitoris: enlarged and rigid through the engorgement of erectile tissue, as during sexual arousal.