The act of cc'ing more senior people to an email thread in order to gain some form of recognition for your efforts. Desperate corporate types clambering up the greasy pole will exhibit this behaviour.
The powerclipper is usually not self-aware enough to use this in an ironic reflexive form, i.e. "I powerclipped senior management so they know how great I am"
Antonym: Powershedding - The emailer sees no need to cc'd everyone on the list so emails directly to the appropriate party. The emailer will usually exhibit high self-esteem.
Noun: "He's a powerclipper"
Verb: "Geez, he powerclipped me in on this banality; it's way below my pay grade"
Ann: "Why did I get this email from Bill?"
Colin: "He's powerclipping his way to the top."