1. (of a person or action) innocent and unsuspecting:"he eyed her with wide, ingenuous eyes"
Word Originlate 16th century: from Latin ingenuus literally ‘native, inborn’, from in- ‘into’ + an element related to gignere ‘beget’. The original sense was ‘noble, generous’, giving rise to ‘honourably straightforward, frank’, hence ‘innocently frank’ (late 17th century).