Definition of "cluster headache" []

• A recurring headache similar to migraine and characterized by severe pain in the eye or temple on one side of the head, watering of the eye, and a runny nose. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.