a. Joining two nonadjacent vertices of a polygon.
b. Joining two vertices of a polyhedron not in the same face.
2. Having a slanted or oblique direction.
3. Having oblique lines or markings.
4. Relating to or being the front left and back right feet or the front right and back left feet of a quadruped.
1. Mathematics A diagonal line or plane.
2. Something, such as a row, course, or part, that is arranged obliquely.
3. A fabric woven with diagonal lines.
4. A virgule.
[Latindiagōnālis, fromGreekdiagōnios, from angle to angle : dia-, dia- + gōniā, angle, corner; see genu-1 in the Appendix of Indo-European roots.]
(click for a larger image)diagonal
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2016 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
The American Heritage Dictionary Blog
Check out our blog, updated regularly, for new words and revised definitions, interesting images from the 5th edition, discussions of usage, and more.
American Heritage Dictionary Products
The American Heritage Dictionary, 5th Edition
The American Heritage Dictionary of Idioms
The American Heritage Roget's Thesaurus
Curious George's Dictionary
The American Heritage Children's Dictionary
The American Heritage Dictionary of Indo-European Roots
The American Heritage Student Grammar Dictionary
The American Heritage Desk Dictionary + Thesaurus
The American Heritage Science Dictionary
The American Heritage Dictionary of Business Terms
The American Heritage Student Dictionary
The American Heritage Essential Student Thesaurus