When your boyfriend proposes to you and it comes as such a complete surprise that you are overcome with emotions and can't even speak, this is an example of when you are speechless.
- incapable of speech; lacking the ability to speak
- temporarily unable to speak; silent, as from shock
- not expressed or expressible in words: speechless terror
- Lacking the faculty of speech.
- Temporarily unable to speak, as through astonishment.
- Refraining from speech; silent.
- Unexpressed or inexpressible in words: speechless admiration.
From speech +"Ž -less