Ĭm'per·cĕp'ti·ble1, a.
a. [Prefix im, not, and perceptible; Fr. & Sp. imperceptible, It. impercettibile.] 1. Not perceptible; not to be apprehended or cognized by the senses; insensible; impalpable; not discernible by the mind; not easily apprehended. Its operation is slow, and in some cases almost imperceptible. Burke. 2. Very small; fine; minute in dimensions; or very slow in progress; as, the growth of a plant or animal is imperceptible.