To excessively or with great apparent pleasure send cell phone text messages. Normally with fervent pecking at the keyboard with dueling thumbs in an almost rhythmic movement. The texter may also be quite unaware of their surroundings, focusing all efforts on proper spelling of cryptic jumbles of letters and acronyms.
He completely lost track of time while thumbsterbating with his girlfriend all night at the party. He would thumbsterbate with his girlfriend at every givenopportunity.
A person whose use of the written English language is very poor due to their constant texting with their thumbs that results in bad spelling and the overuse of extreme abbreviations like LOLROTF.
This paper is so poorly written it must be the work of a thumbster with blisters!
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.