...

Triple Dots/... is the expression of either:
1. being disappointed at someone
2. being surprised or not being surprised by how stupid someone is
3. showing someone that their comment in a discussion was either:

a) not needed at all

b) not sharing any relation to the discussion itself

Person 1: "yo fam the moon is made out of cheese lololol"
Person 2: "..."
Person 1 : "what"
Person 2: "you are showing your lower level of intellect"