1. Violation of allegiance toward one's country or sovereign, especially the betrayal of one's country by waging war against it or by consciously and purposely acting to aid its enemies.
2. A betrayal of trust or confidence.

[Middle English, from Anglo-Norman treson, from Latin trāditiō, trāditiōn-, a handing over. See tradition.]

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.