or french curve
a flat drafting instrument, usually consisting of a sheet of clear plastic, the edges of which are cut into several scroll-like curves enabling a draftsperson to draw lines of varying curvature.
Origin of French curve
First recorded in 1880–85
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
British Dictionary definitions for french curve
a thin plastic sheet with profiles of several curves, used by draughtsmen for drawing curves
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012