To "phatwack" is when you slap your own or another persons vagina repetitively instead of penetrating.

It is a modern form of lesbian sexual intercourse.
"Did you phatwack her?"

"On New Year's Day i phatwacked, was real great!"

"So much room for phatwacking in comfy pants!"

"I feel like phatwacking would hurt if you were sober.."
by moogledefined August 11, 2013
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