What is "bitangent"

Bitangent \Bi*tan"gent\, a. [Pref. bi- + tangent.] (Geom.) Possessing the property of touching at two points. -- n. A line that touches a curve in two points.

n. (context mathematics English) A line that is tangent to a curve at two points

In mathematics, a bitangent to a curve C is a line L that touches C in two distinct points P and Q and that has the same direction as C at these points. That is, L is a tangent line at P and at Q.