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1.
A sexual act where the partner massages a man's anus, grundle, and balls with his/her tongue.

"Lunch Under the Pipes" literally bridges the gap between the anus and the balls thus affording each partner maximum pleasure.

For a Similar Definition See tossed salad
"Last night, Thurgood and I were watching a movie and I ended up having some lunch under the pipes. It was pretty great."
by ResIpsa March 10, 2010