Dictionary
im•per•cep•ti•ble
Pronunciation: (im"pur-sep'tu-bul), [key]—
adj.
1. very slight, gradual, or subtle:
the imperceptible slope of the road.
2. not perceptible; not perceived by or affecting the senses.
—
n.
something not capable of being perceived by the senses:
metaphysical speculation about imperceptibles. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.