agrin,adv., prop.phr.|əˈgrɪn| [a prep.1 of state, in, on + grin.] On the grin; in a grinning attitude. 1847Tennyson Princess v. 510 His visage all a-grin.1849C. Brontë Shirley I. iii. 47 His hard features were revealed all agrin and ashine with glee.