once in a lifetime
US /wʌns ɪn ə ˈlaɪfˌtaɪm/
UK /wʌns ɪn ə ˈlaɪfˌtaɪm/

1.
sekali seumur hidup, langka
an event or opportunity that is very rare and unlikely to happen again in a person's life
:
•
Seeing the total solar eclipse was a once in a lifetime experience.
Melihat gerhana matahari total adalah pengalaman sekali seumur hidup.
•
This opportunity to travel the world is truly a once in a lifetime chance.
Kesempatan untuk berkeliling dunia ini benar-benar peluang sekali seumur hidup.