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1.
noun/verb.
plural form: Happy Cacti

When a guy who has participated in "No Shave November" goes down on a girl to eat her out. The rubbing of the stubble against her vagina would be analogous to a cactus rubbing against her flesh. In an added twist, the female has a deflated balloon inserted in her vagina. As the balloon is blown up by the male partner's mouth play, the balloon expands, causing a tickling sensation.

In a male-to-male variation, substitute the vagina for an anus.
Hunter made his girlfriend scream in pain and delight as he gifted the Happy Cactus upon her.

Mitchell's boyfriend made him scream out in pain and unexpected delight as Mitchell was surprise Happy Cactus'ed.
by CPT Morgan, Ph.D. November 30, 2010