Named for the motion as well as the signature Hitler mustache the motion creates, this euphemism involves an underhanded "zig heil" arm movement with an end result on your significant other having a Hitler 'stache.
Said to your friends at work in an extremely roundabout way:

"While we were experimenting with the glitter sack the previous day, I am currently trying to surprise her with an Underhanded Hitler."
by The Other B Money November 7, 2008
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