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1.
Can be used to describe many sexual acts that involve exchanging fluids without having intercourse. (comes from the computer term where keys are exchanged in encryption)like the cleveland steamer.
"man i just got back from shannons.....talk about a good diffie hellman....the whole place was wet."

"she wouldnt fall for my famous line so i had to give her the diffie hellman and make sure she swallowed."
by Scooter May 07, 2004