lifetime

UK: /ˈlaɪftaɪm/ US: /ˈlaɪfˌtaɪm/ ,(līf′tīm′)

WordReference Random House Learner's Dictionary of American English © 2025

life•time /ˈlaɪfˌtaɪm/   n. [countable]

1. the amount of time that a person stays alive or that something continues;
   the term of a life:
   hoped to see peace within our lifetime.
2. a very long time:
   We waited a lifetime for the doctor's report.

adj. [before a noun]

3. for the length of a person's life:
   a lifetime membership.

Idioms

4. of a lifetime, [after a noun] most memorable:
   the vacation of a lifetime.

WordReference Random House Unabridged Dictionary of American English © 2025

life•time  (līf′tīm′), n. 

1. the time that the life of someone or something continues;
   the term of a life:
   peace within our lifetime.
2. Physics See mean life. 

adj. 

3. for the duration of a person's life:
   He has a lifetime membership in the organization.

• Middle English liftime. See life, time 1175–1225

Collins Concise English Dictionary © HarperCollins Publishers::

lifetime / ˈlaɪfˌtaɪm/ noun

1. the length of time a person or animal is alive
2. (as modifier): a lifetime supply
3. the length of time that something functions, is useful, etc
4. the average time of existence of an unstable or reactive entity, such as a nucleus, excited state, elementary particle, etc; mean life