un·tir·ing 
/ˌʌnˈtaɪrɪŋ/ adjective
/ˌʌnˈtaɪrɪŋ/ adjective [more untiring; most untiring] : working very hard with a lot of energy for a long time : never seeming to get tired
▪ the rescuers' untiring efforts ▪ She is an untiring [=tireless] advocate for the poor.
▪ the rescuers' untiring efforts ▪ She is an untiring [=tireless] advocate for the poor.
