形容词

1. 察觉不出的;感觉不到的;难以察觉的
Something that is imperceptible is so small that it is not noticed or cannot be seen.

1. impossible or difficult to perceive by the mind or senses

e.g. an imperceptible drop in temperature
an imperceptible nod
color is unperceivable to the touch

Synonym: unperceivable