Definition of unflagging:
continuing, unwearying, foolproof, untiring, indefatigable, unbroken, inexhaustible, endless, dynamic, indefinite, constant, continual, unceasing, continuous, hardworking, tired, continue, weariless, active, energetic, unwearied, forever, tireless, industrious, permanent, unfailing.
- persevering (part of speech: adjective)
tenacious (part of speech: adjective)
- "Half Portions", Edna Ferber.
- "Complete State of the Union Addresses from 1790 to the Present", Various.
- "Seeds of Pine", Janey Canuck.