unflagging

It was his business acumen, his own unflagging zeal for the creative business solution, that had freed Sam to do this.

Often the reverie rolled on deep into the night, an unflagging, unredundant product of the raconteurial mind.

Perhaps no group has been as unflagging in its back of Israel than evangelicals in the U.S.

Unflagging, un-flag′ing, adj. not flagging or drooping: maintaining strength or spirit.