The definition of relentless is persistent or unyielding.
Having no foreseeable end:
Not stopping, relaxing, or slackening; incessant; persistent
Find another word for on-and-on. In this page you can discover 11 synonyms, antonyms, idiomatic expressions, and related words for on-and-on, like: relentless, continuously, forever, never-ending, time-after-time, time-and-time-again, uninterruptedly, unremitting, without stopping, constantly and without a break.