1. An ancient Celtic feast celebrating the end of harvest and the beginning of winter, marked by bonfires and sacrifices and by the propitiation of gods who were believed to become visible and play tricks on their worshipers.
2. The period during which this feast was held, usually the evening of October 31 and the day of November 1.
[Irish Samhain, from Old Irish samain; see sem-2 in the Appendix of Indo-European roots.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 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.