\Tri*sect"\, v. t. [imp. & p. p. {Trisected}; p. pr. & vb. n. {Trisecting}.] [Pref. tri- + L. sectus, p. p. of secare to cut. See {Section}.] 1. To cut or divide into three parts. 2. (Geom.) To cut or divide into three equal parts.