unflagging
1. [ adjective ] showing sustained enthusiastic action with unflagging vitality
Synonyms: tireless indefatigable unwearying
Examples:

"an indefatigable advocate of equal rights" "a tireless worker" "unflagging pursuit of excellence"

Related terms: energetic
2. [ adjective ] unceasing
Synonyms: unfailing
Examples:

"unfailing loyalty" "unfailing good spirits" "unflagging courtesy"

Related terms: constant
Similar spelling:   unpleasing
  unflattering
  unblushing
  unblinking
  unobliging
  unblushingly
  unblinkingly
  unifoliate
  unblushinghly