To knock around the nozzle of a gas pump while it's still in the tank to get the last bit of gas out so it doesn't leak on your car or your shoes when you take it out.
Mom to young son who is filling her car with gas: "Don't forget to 'spank the nozzle'."
When you're doing a chick in the ass and she gets diarrhea and it squirts out all over the place. Kind of like when you stick your thumb in the end of a hose nozzle and the water shoots out forcefully.
Rich: "So how was fuckin Lauren last night? I could hear it going down in the living room."
Adam: "Well it was good till I stuck it in her ass. Then i got the old Thumb in the Hose Nozzle action and spent the rest of the night cleaning up your leather couches."
See also:
stroking the sausage slapping the meat petting the weasel
spanking the monkey
flogging the dolphin
tickling the pickle
whacking the mole
playing the skin flute
cream-filling the donut