The briefest possible act of sexual intercourse. There is no "pumping" involved - just insertion, ejaculation, and withdrawal.
Although very similar physically to a "one-pump wonder," but a flu shot is different because it is a deliberate act meant to save time. A flu shot requires training to accomplish correctly. A flu shot is a valuable scheduling tool.
Men generally enjoy giving flu shots more than women enjoy receiving them, but with discipline women should be able to train their bodies to orgasm from a single flu shot.
I joined the mile high club when I gave my girlfriend a flushot in the bathroom right before the plane landed.
While having sex doggy style, the person doing the jack hammering chugs a gallon of milk. The gyration of the body with the souring of the milk in the stomach will induce vomiting. This will need to be timed perfectly with ejaculation. While the shot goes inside of the vagina, the flu like vomit goes all over the back.
"Last night i gave my girl a flu shot and i dont think that she liked me cumming inside her or my puke on her back."
The guilt projected onto a person that doesn't want to or believe in taking the flu shotvaccine.
You say "No" meaning "I don't want you to inject me with formaldehyde & mercury" and the nurse gives you the flu shot guilt by sending you a look like you just said "there's no such thing as God."