Unable to speak, especially as the temporary result of strong emotion or shock. “I am speechless.” Similar: silent, unspoken, unexpressed, wordless, unsaid, unvoiced, voiceless, Lost for words, at a loss for words, dumbfounded, thunderstruck, dumbstruck, shocked, struck dumb, bereft of speech, tongue-tied, unable to get a word out, inarticulate, mute, dumb, shell-shocked, astounded, aghast, amazed, dazed, flabbergasted, mum, knocked/hit for six, gobsmacked, dumbstricken, mumchance, obmutescent.