To divide into three parts or sections: Branching off or parting into three directions: While following the map, Bernice could see that the freeway trifurcated in about three miles, but she knew she needed to stay in the middle lane because she did not want to travel in the right or the left lanes.

A reference to something that has three attachments or segments: The key ring which Sammy made in his metal shop was a trifurcated design, with three separated parts, one for keys, one for an emergency whistle, and one for a small flashlight.

This trifurcated example came from Google images.