Pronunciation: (im-pal'pu-bul), [key]
1. not palpable; incapable of being perceived by the sense of touch; intangible.
2. difficult for the mind to grasp readily or easily: impalpable distinctions.
3. (of powder) so fine that when rubbed between the fingers no grit is felt.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.