nerve·less (nûrv?l?s)adj.1. Lacking strength or energy; spiritless; weak.2. Lacking courage; cowardly.3. Calm and controlled in trying circumstances; cool.nerve?less·ly adv.nerve?less·ness n.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.