1. Formed by or having two plane faces; two-sided.
2. Relating to, having, or forming a dihedral angle.

1. Mathematics.
   1. A dihedral angle.
   2. A dihedral group.
2. Aeronautics. The upward or downward inclination of an aircraft wing from true horizontal.

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.