adj. 25B6; adjective
the unrelenting heat : CONTINUAL, constant, continuous, relentless, unremitting, unabating, unrelieved, incessant, unceasing, endless, unending, persistent.
an unrelenting opponent : IMPLACABLE, inflexible, uncompromising, unyielding, unbending, relentless, determined, dogged, tireless, unflagging, unshakeable, unswerving, unwavering.
intermittent.