unflagging

Adjective
  1. Showing sustained enthusiastic action with unflagging vitality (synset 300878228)
    "an indefatigable advocate of equal rights"; "a tireless worker"; "unflagging pursuit of excellence"
  2. Unceasing (synset 300586322)
    "unfailing loyalty"; "unfailing good spirits"; "unflagging courtesy"

Found on Word Lists

Other Searches