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1.
When older couples decide to have sex, they usually describe it {to friends of the same age of course} as "nifty". Thus sex between old people is nifty sex.
70 year old Tom was telling his life long friend {Ed } of his wild night with his wife when he said smiling, "Yeah, that was really nifty sex last night."

"Dude! Did your grandpa just describe his "nifty sex" to us?"
"Yeah, I think he did because, grandma is turning red and I want to puke on my shoes....."
by Bob the CatDog June 07, 2011