It was a once-in-a-lifetime experience.

Meaning

The experience was very special and unlikely to happen again.

Examples

• John: 'Traveling to Antarctica was incredible!'
• Alice: 'It sounds like <b>it was a once-in-a-lifetime experience</b>.'
• John: 'Definitely, <b>it was a once-in-a-lifetime experience</b>.'
• Alice: 'Meeting that famous author was amazing.'