To possess large arms; when one's arms are particularly large.... for instance after lifting weights. Derived from the word "guns" (or arms).
Tamara: "Nick, where have been all fukkin' day?"
Nick: "Chill out, big girl. I've been pumpin' some iron."
Tamara: "I can tell. You look all gunned up, you handsome devil."
Brought to public attention by Bob Woodward and Carl Bernstein in the book on the fall of Richard Nixon, All The President’s Men, ratfucker was Nixon’s term for a political operative who sows chaos among opponents; an agent provocateur. It is thought to have originated among campus political rivalries at USC, and seems to have some usage in the US military.
Along with Nixon’s other ratfuckers, Roger Stone caused fights at otherwise peaceful Democratic Party protests to generate a false narrative that the Democrats were violent and dangerous.