Main entry: 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
Antonyms: perceptible
Definition: capable of being perceived by the mind or senses
Definition: able to feel or perceive
Antonyms: discernable, discernible
Definition: perceptible by the senses or intellect
Definition: capable of being perceived; especially capable of being handled or touched or felt