insomniac /ɪnˈsɒm.ni.æk/adjective 1noun 1forms 3 adjective1 •Suffering from or pertaining to insomnia.By 9 A.M., however, all but the most insomniac of the night owls were taking a catnap. — 1963 noun1 •One who suffers an inability or difficulty sleeping; a sufferer from insomnia.Leave my door open just a crack (please take me away from here) 'Cause I feel like such an insomniac (please take me away from here) — 2009 formsinsomniacs · more insomniac · most insomniac