(a.) Not using words; not speaking; silent; speechless.

anaudic aphasic aphonic breathless brief brusque close close-lipped close-tongued closemouthed concise curt dumb dumbfounded dumbstricken dumbstruck economical of words implicit implied inarticulate indisposed to talk inferred laconic mum mute quiet reserved reticent short silent snug sparing of words speechless stricken dumb tacit taciturn terse tight-lipped tongue-tied tongueless uncommunicative undeclared understood unexpressed unloquacious unmentioned unproclaimed unpronounced unpublished unrecorded unsaid unspoken unsung untalkative untalked-of untold unuttered unvoiced unwritten voiceless word-bound