life·time

/ˈlaıfˌtaım/ noun, pl -times [count]

1 a : the time during which a person is alive

Four editions of the book were printed in his lifetime. [=during his life]

She has had a lifetime of hard work. [=she has worked hard all her life]

a lifetime spent traveling the world

I don't think it will happen in our lifetime. [=the time when we are alive]

She owns enough shoes to last (her) a lifetime. [=to last for the rest of her life]

the thrill of a lifetime [=a great thrill; the most exciting moment or event of a person's life]

This is the opportunity of a lifetime. = This sort of opportunity comes along once in a lifetime. [=this is a very rare opportunity]

— often used before another noun

He won a lifetime supply of ice cream. [=free ice cream for the rest of his life]

She was presented with a lifetime achievement award. [=an award for all the work she has done in her life]

a baseball player's lifetime batting average [=batting average measured over a baseball player's full career]

1 b : a very long time

It would have taken me a lifetime to read all those books.

Childhood seems a lifetime ago now!

2 : the time during which something lasts or is useful

a chemical with a lifetime of only a few minutes

the lifetime of a planet/star/comet