at a loss for words
(idiomatic) Having nothing to say; not knowing what to say; stunned to the point of being speechless.
She was at a loss for words when she saw the number of people who had come to grieve for her husband.
I am at a loss for words to describe my lack of eagerness to go there. Charles Stross
The mark of a true politician is that he is never at a loss for words because he is always half-expecting to be asked to make a speech. Richard Nixon
I'm at a loss for words. But even my loss is amplified. Talib Kweli
More and more I find myself at a loss for words and didn't want to hear other people talking either. Their conversations seemed false and empty. I preferred to look at the sea, which said nothing and never made you feel alone. Paula McLain
A man with a sense of humor is never at a loss for words or action. Somali Proverb
Women are never at a loss for words. German Proverb