COX-2 inhibitorn. Any of a class of nonsteroidal anti-inflammatory drugs that selectively block prostaglandin formation so as to cause minimal gastrointestinal side effects.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.