double tangent[¦dəb·əl ′tan·jənt]
A line which is tangent to a curve at two distinct noncoincident points. Also known as bitangent.
Two coincident tangents to branches of a curve at a given point, such as the tangents to a cusp.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.