1. The repeated typing of 'qwertyfuck' into someone's computer, with the intent of annoying them.
2. Inserting 'qwertyfuck' into an important piece of work, preferably not your own, in order to confuse the reader or get the writer into trouble.
3. The general spamming of someone's keyboard, by hitting random keys.
'Joe's left the room, let's qwertyfuck the hell out of him.'
'Can you stop qwertyfucking me, this is a really important piece of work!'