from The American Heritage® Dictionary of the English Language, 4th Edition
- adj. Impossible or difficult to perceive by the mind or senses: an imperceptible drop in temperature.
- adj. So subtle, slight, or gradual as to be barely perceptible: an imperceptible nod.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. Not perceptible, not detectable, too small in magnitude to be observed.
from the GNU version of the Collaborative International Dictionary of English
- adj. Not perceptible; not to be apprehended or cognized by the senses; not discernible by the mind; not easily apprehended.
from The Century Dictionary and Cyclopedia
- Not perceptible; that cannot be perceived.
- Incapable by nature of affecting the senses.
- Too minute, fine, gradual, subtle, or evanescent to be discerned by the senses; producing an excitation of the nerves less than the threshold of sensation. See threshold.
- n. That which cannot be perceived with the naked eye, or realized by sensation.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- adj. impossible or difficult to perceive by the mind or senses
Middle English, from Middle French, from Medieval Latin imperceptibilis (Wiktionary)