adj.千载难逢的;
例句:
Nearly everyone must endure at least once in a lifetime.
几乎每个人一生中至少要体验一次.
Since it's a once-in-a-lifetime thing, I want everything to go right.
一生一次的事情, 总是弄得正正经经的.
It's a once in a lifetime chance.
这是一生难得的机会.