When you're feeling lost for words, it can be helpful to have some synonyms on hand to express your feelings. One such synonym is speechless, which implies a complete inability to speak. Another option is tongue-tied, which suggests a difficulty in finding the right words or expressing oneself coherently. Other possible synonyms include dumbfounded, flabbergasted, and astonished, all of which convey a sense of shock or disbelief. Alternatively, you could use the phrase "at a loss for words", which is similar in meaning to "lost for words" but may sound a bit more formal. Whatever phrase you choose, it's important to remember that it's okay to not always have the right words at your fingertips.