unflagging
adjective uk/ʌnˈflæɡ.ɪŋ/ us/ʌnˈflæɡ.ɪŋ/
（精力、兴趣、热情等）永不减弱的，不懈的，持久的
If a quality, such as energy, interest, or enthusiasm, is unflagging, it never becomes weaker.
He thanked Tony for his unflagging energy and support. 他感谢托尼坚持不懈的努力和支持。
Synonyms: indefatigable tirelessuntiringunwavering (NOT CHANGING)
Opposites: faltering (FAILING)flaggingwavering