The act of initiating and finishing a hand job in one, earth-shatteringly pleasurable pump. It cannot be completed more than once in any 24 hour span, or the receiver will die a horrible, agonizing death.
Feeling spicy, the middle-aged man asked for an OPHJ. The crazy lady obliged...steadied herself, and in one quick motion finished the man off with a loud yell followed by a quick jerking motion. Groaning, the man immediately fell asleep on the floor. Thus, she had performed the fabled one pump hj.
A simile/idiom similar in meaning to "one man's trash is another man's treasure" only, in this case, it means that what is funny to one person may be offensive to someone else.
Tom: "Man, I told this hilarious joke last night. Everyone laughed but Bob. He was a douche and said the joke was offensive."
Dick: "Don't worry about it, dude. One man's LOL is another man's WTF?"