nerve agent n. Any of various poisonous compounds, dispersed in vapor or aerosol form, that interfere with the functioning of nerves by inhibiting acetylcholinesterase. Also called nerve gas. 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.nerve agentA potentially lethal chemical agent which interferes with the transmission of nerve impulses.Dictionary of Military and Associated Terms. US Department of Defense 2005.