Entire Life, A Lifetime, All Through Life, One Existence, A Generation, An Age
Noun and の adjective
いっしょう
このゆびわは、一生、大切にします。
I’ve taken care of this ring my whole life.
わたしの父は、しぬまで一生どくしんでした。
My father remained single all his life.
一生かけて償います。
I’ll make up for it with my life.
One life is all you get. It's your whole life.
This is a jukugo word that uses the on'yomi readings of the kanji. You didn't learn this reading for 生 though, so here's a mnemonic to help you:
Who has been in charge of you your whole life? The shogun (しょう). He owns everyone and that's how it will stay for your entire life.