1. extremely rare; exceptionally uncommon

Examples

• The museum acquired an ultrarare manuscript from the 12th century.
• This ultrarare butterfly species has only been spotted three times in the wild.
• Collectors pay enormous sums for ultrarare baseball cards from the 1950s.
• The ultrarare mineral was discovered in only one location on Earth.
• Scientists were thrilled to observe the ultrarare astronomical event.
• The ultrarare vintage wine sold for a record price at auction.