What is to enter anew or again. Reëntering angle, an angle of a polygon pointing inward, as a, in the cut. -- Reëntering polygon, a polygon having one or more reëntering angles called?

reenter — To enter anew or again. Reëntering angle, an angle of a polygon pointing inward, as a, in the cut. -- Reëntering polygon, a polygon having one or more reëntering angles. (Webster's 1913.)