noun
natural lifespan; allotted years
Refers to the full, natural length of a person's life as determined by heaven or fate. Often used in the phrase 天寿を全うする (to live out one's natural life).
祖父は天寿を全うして、穏やかに亡くなった。
My grandfather lived out his natural lifespan and passed away peacefully.
寿命 is the general word for 'lifespan' or 'life expectancy,' while 天寿 carries a nuance of a heaven-ordained, natural span of life.
Compound of 天 (heaven) and 寿 (longevity). The exact historical derivation is uncertain, but the word has long been used to mean the natural lifespan granted by heaven.