Top Definition
Taking all three major branches of science (Biology, Chemistry, and Physics) at the same time in high school.
"I don't know which science I'll study in college, so I'll take tri sci to expand my options."
by ninjaraccoon19 December 08, 2013
1 more definition
A rendition of the widely known sexual act known as "scissoring", which typically consists of two participants. However, when a third person daringly decides to join in, it is referred to as the "Tri-Sci", due to the positioning/layout of the three participants and their genitalia. This act can be performed by three females, two males and one female, or three males. Although many have attempted the Tri-Sci with two females and one male, it has proved to be an impossible task.
-Are you two scissoring?!?
-Yeah! wanna join in?
-I don't know if I'm flexible enough to pull off the Tri-Sci, but let's go for it!
by RICHvcl April 16, 2011

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