trilinear[trī lin′ē ər]
trilinear definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
of, enclosed by, or involving three lines
Origin: tri- plush linear
trilinear definition by American Heritage Dictionary
Relating to, having, or bounded by three lines.