The Collaborative International Dictionary
Trisection \Tri*sec"tion\, n. [Cf. F. trisection.] The division of a thing into three parts, Specifically: (Geom.) the division of an angle into three equal parts.
Wiktionary
n. (context mathematics English) The division of an angle into three equal parts
Usage examples of "trisection".
But if he was very persistent, and the chase became too hot, it was easy to draw a red herring across the track, the aforesaid red herring generally taking the shape of one of those venerable questions, which, like the trisection of an angle, or the quadrature of a circle, or the secret of perpetual motion, shall never be finally solved.
Before that it had been a compendium of various failed angle trisection theorems, and before that, an incredibly long list of the powers of ten and the various words that had been invented to describe the astronomical numbers those powers represented.
He asserts that as he cannot find any solution to the problem it must have something to do with the squaring of the circle, the duplication of the cube, or the trisection of an angle.