1. extending back beyond the reach of memory, record, or tradition; ancient beyond reckoning
Usage: often used in the phrase 'time immemorial' to mean a time so distant that its beginning is unknown or forgotten

Examples

• The tradition of lighting candles at winter solstice dates back to time immemorial.
• These mountains have stood immemorial, unchanged for millions of years.
• The practice has been followed since time immemorial in this village.
• Immemorial customs governed the way the ceremony was conducted.
• The forest seemed immemorial, as if it had always existed in that form.