The act of pressing the "divert" button on a mobile phone in order to avoid talking to someone. Invariably the caller will realise that he or she has been "thumbed", and therefore deliberately rejected. Thumbing is often intended to be a humiliating act, a snub that establishes dominance in a relationship: the caller is the supplicant, and is wholly at the mercy of the person being called.

When you eat dirt for the first time and leave your family to build a shack in the woods