1. Of, relating to, or being a trigraph.
2. Of, relating to, or being a substitution or procedure by groups of three characters or elements at a time in encoding, decoding, or cryptanalysis.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.