Definition of "relentless"

She sniffed, too, comprehendingly, and fixed her son with a relentless eye.

1930, Norman Lindsay, Redheap, Sydney, N.S.W.: Ure Smith, published 1965, page 111

In Clintonworld, the reaction to Grassley’s relentless assault on Huma is one of resignation.

2016 January 31, “Is Huma Abedin Hillary Clinton’s Secret Weapon or Her Next Big Problem?”, in Vanity Fair, retrieved 21 January 2016