Synonyms: imperceptible, unperceivable
Definition: impossible or difficult to perceive by the mind or senses
Usage: an imperceptible drop in temperature; an imperceptible nod; color is unperceivable to the touch
Similar words: impalpable
Definition: not perceptible to the touch
Usage: an impalpable pulse
Similar words: incognizable, incognoscible
Definition: incapable of being perceived or known
Similar words: indiscernible, insensible, undetectable
Definition: barely able to be perceived
Usage: the transition was almost indiscernible; an almost insensible change
Similar words: subliminal
Definition: below the threshold of conscious perception
Similar words: unobservable
Definition: not accessible to direct observation