it stands for "talking to myself" , when that person you're talking to on-line doesn't talk, so you say ttms, so that they realise they've ditched you.
Roro: i thinkstar wars was really good! have you seen it?
Vicky: ...
Roro: ttms ¬¬
when you're holding up your phone and making faces at it, as though you are taking a selfie, but you're really taking a picture of the person across from you or the wall or anything else that seems interesting but you don't want to be caught dead taking a picture of.
This action is often made more convincing by wiggling the eyebrows or opening the mouth, to pretend you're trying to get a Snapchat filter to work.
FRIEND A: "Did you just take a stealthie of me?"
FRIEND B (turning phone around): "no I was just using snapchat's new filter, see?"