The act of texting an acquaintance with a blank text. The implication of this is that you would blank said acquaintance if you saw them walking along on the street and they said hi to you. Blankies are used to show a general dislike or anger towards a person.
The effect is doubled if the person on the receiving end owns an old phone which can only store a limited number of texts (e.g. a Nokia 3310).
Person 1: Oh shit man.
Person 2: What's up, James?
Person 1: Jenny just sent me a blanky.
Person 2: Ha, she must really hate you.