1. the duration of a person's life: "a reward for a lifetime's work"Similarlifespanlifedaysduration of lifeallotted spancourse of lifetime on earthexistenceone's timeone's careerone's threescore years and tenthis mortal coilinformal:one's born days
▪ the duration of a thing's existence or usefulness: "fifteen shops closed during the lifetime of the scheme"Similardurationlifeactive lifeexistencelife expectancyfunctioning periodperiod of effectiveness/usefulness/validity/efficacy
▪ a very long period of time:"five weeks was a lifetime, anything could have happened"Similarall one's lifea very long timean eternityhoursdaysmonthsyearsaeonshours/days/months on endinformal:ages (and ages)an age