temporarily deprived of speech by strong emotion, physical weakness, exhaustion, etc.

speechless with alarm.

characterized by absence or loss of speech

speechless joy.

lacking the faculty of speech; dumb.

not expressed in speech or words

speechless compliments.

refraining from speech.

adjective

articulate , communicative , responsive

adjective

aghast , amazed , aphonic , astounded , buttoned up , clammed up , close-mouthed , cool * , cool as cucumber , dazed , dumb , dumbfounded , dumbstruck , inarticulate , mum , mute , not saying boo , reserved , shocked , silent , taciturn , thunderstruck * , tight-lipped * , tongue-tied * , uncommunicative , unflappable , voiceless , wordless , aphasic