incommunicable

1. Impossible to be transmitted; not communicable: an incommunicable disease.
2. Incommunicative: an executive who was maddeningly incommunicable.

adjective

1. Not speaking freely or openly: close, close-mouthed, incommunicative, reserved, reticent, silent, taciturn, tightlipped, uncommunicable, uncommunicative. See restraint/unrestraint, sounds/pleasant sounds/unpleasant sounds/neutral sounds or silence.
2. That cannot be described: indefinable, indescribable, ineffable, inexpressible, undescribable, unspeakable, unutterable. Idioms: beyonddescriptionwords, defying description. See words.