1) Agape 2) Aghast 3) At a loss 4) At a loss for words 5) Awed 6) Dumb 7) Inarticulate 8) Lost for words 9) Mum 10) Mute 11) Silent 12) Surprised 13) Tongue tied 14) Unarticulate 1) Amazed 2) Dumb 3) Dumbfounded 4) Inarticulate 5) Mum is amazed 6) Not conveyed by words 7) Silenced 8) Unable to speak temporarily 9) Unarticulate 
[play] Speechless is a 2011 play by British playwrights Linda Brogan and Polly Teale. It was based on The Silent Twins by Marjorie Wallace, telling the story of June and Jennifer Gibbons. Its premiere was a national tour of the UK from 20 September to 26 November 2011, in a Shared Experience-Sherman Cymru co-production - venues included the...
• (a.) Destitute or deprived of the faculty of speech. • (a.) Not speaking for a time; dumb; mute; silent.
Speech'less adjective 1. Destitute or deprived of the faculty of speech. 2. Not speaking for a time; dumb; mute; silent. « Speechless with wonder, and half dead with fear.» Addison. -- 
[adj] - unable to speak temporarily
adjective unable to speak temporarily; `struck dumb`; `speechless with shock`
temporarily incapable of speaking