Synonyms for imperceptible

Adjective

1. imperceptible (vs. perceptible), unperceivable, impalpable, incognizable, incognoscible, indiscernible, insensible, undetectable, subliminal, unobservable, impalpable, inaudible#1, unhearable, invisible#1, unseeable

usage: impossible or difficult to perceive by the mind or senses; "an imperceptible drop in temperature"; "an imperceptible nod"; "color is unperceivable to the touch"