Untiring(adjective)
Continuing to do something for a long period of time with a lot of effort and/or enthusiasm.
Hindi meaning:अथक
Synonyms: Tireless, Undefeatable, Persistent, Unfailing
Antonyms: Failing, Tiring, Irresolute
Example: It seems like an untiring campaigner for human rights.
Trick to remember: Jo tired nhi wo untiring hai. 
