The Oxford Thesaurus An A-Z Dictionary of Synonyms - ingenuous adj.

1) na‹ve, simple, innocent, unsophisticated, childlike, suggestible, artless, sincere, genuine, trusting, guileless, natural, straight, uncomplicated, (fair and) square, honest, fair, just, open, undeceitful, unaffected, undeceptive, undissembling, unfeigning, (open and) above-board, Colloq on the level: What ideas have you been implanting into the mind of this ingenuous young girl? 2 frank, candid, open, trustworthy, honourable, forthright, direct, straightforward, four-square, honest, outspoken, blunt, bluff, bold, unreserved, free, uninhibited, unabashed: I shall be ingenuous enough to confess that what you heard about me is true.