in·still / inˈstil/ (Brit. also in·stil) • v. [tr.] 1. gradually but firmly establish (an idea or attitude, esp. a desirable one) in a person's mind: how do we instill a sense of rightness in today's youth?2. put (a substance) into something in the form of liquid drops: she was told how to instill eye drops.DERIVATIVES: in·stil·la·tion / ˌinstəˈlāshən/ n.in·still·ment n.