not palpable; incapable of being perceived by the sense of touch; intangible.

difficult for the mind to grasp readily or easily

impalpable distinctions.

(of powder) so fine that when rubbed between the fingers no grit is felt.

adjective

believeable , palpable , perceptible , substantial , tangible , understandable

adjective

airy , delicate , disembodied , fine , imperceptible , imponderable , imprecise , inappreciable , incorporeal , indiscernible , indistinct , insensible , insubstantial , nebulous , shadowy , tenuous , thin , unapparent , unobservable , unperceivable , vague , indistinguishable , intangible , invisible , unnoticeable