interj.
Used to wish good health to a person who has just sneezed.
[German, health, from Middle High German gesuntheit, from gesunt, healthy, from Old High German gisunt.]
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.