"......" is silence with some meaning implied....it can either be just ignoring the person, or restraining your thoughts when you see someone saying or doing something which you consider crazy or nuts....sorta like "uhhhhhh....." "um....ya...right." in your head....
Or it could mean like you don have a smart reply to counter what someone said....
Take the Barret, Tifa, Cloud, running up the stairs scene when they sneak into the Shinra building via the maintenance section/fire escape
After climbing many floors
Barret: Damn it. I've had it!. I''m going back!
Tifa: It'll take just as long to go back.
Barret: ........
Obviously Barret is grumbling to himself silently in his head here....