is similar to: close, closelipped, closemouthed, secretive, tightlipped | deadpan, expressionless, impassive, poker-faced, unexpressive | incommunicado | inexpressive | mum, silent | unpronounceable, unutterable.

see also: inarticulate, unarticulate | taciturn.

is the opposite of: communicative, communicatory.

derivation: uncommunicativeness.