Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio.
having three sides or faces: a trihedral angle
Origin: tri- plush -hedral
a figure formed by three lines, each in a different plane, that intersect at a point
Used by arrangement with John Wiley & Sons, Inc.
The American Heritage® Dictionary of the English Language, 4th edition Copyright © 2010 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Having or formed by three planes meeting at a point.noun