1. A wind system that influences large climatic regions and reverses direction seasonally.
2. 1. A wind from the southwest or south that brings heavy rainfall to southern Asia in the summer.
   2. The rain that accompanies this wind.

[Obsolete Dutch monssoen, from Portuguese monção, from Arabic mawsim, season, from wasama, to mark.]

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.