不知疲倦的；坚持不懈的；永不减弱的If someone has untiring energy, interest, or enthusiasm, their energy, interest, or enthusiasm never becomes weaker.
We'd like to thank George for his untiring efforts on our behalf. 对于乔治为我们做出的不懈努力，我们表示感谢。
Synonyms: indefatigable tirelessunflagging