relentlessness
re·lent·less·ness
noun
1.
mercilessness characterized by an unwillingness to relent or let up
- “the relentlessness or their pursuit”
Origin
From relentless + -ness.
Related words
Broader terms
WordNet 2.1 (Princeton University). Wiktionary (CC BY-SA). WordNet 2.1 Copyright Princeton University. All rights reserved. Wiktionary content is available under the Creative Commons Attribution-ShareAlike Licence.