Earlier today, a student of mine was telling me a story about how his colleague, upon seeing him wearing an over-the-top jacket, was so surprised that she couldn't say anything.
Question: Which expression would you have said?
"My colleague was tongue-tied when she saw me wearing such an extravagant jacket"
"My colleague was speechless when she saw me wearing such an extravagant jacket"
I'd always thought that the two were synonyms, but Merriam Webster defines tongue-tied as "unable to speak because you are nervous or shy" and speechless as "unable to speak because of anger, surprise, etc.", so I'd probably be more inclined to use speechless in this situation.
However, Random House Kernerman Webster's College Dictionary has a broader definition of tongue-tied ("unable to speak, as from shyness, embarrassment, or surprise"), which seems to suggest that speechless and tongue-tied are synonyms.
Your thoughts? How would you use speechless and tongue-tied?