IPA: /ʌnˈkʌmən/
KK: /ʌnˈkɑːmən/
Something that is not frequently found or seen; it is rare or unusual.
Finding a four-leaf clover is quite uncommon.
Comparative: more uncommon
Superlative: most uncommon
Uncommon → It is formed from "un-" (meaning not) and "common" (from Old French *comun*, meaning shared by all or usual). The word "uncommon" means not usual or not shared by all, indicating rarity.
Think of 'not' ('un-') and something that is 'shared by all' ('common') to remember that 'uncommon' refers to something that is rare or not usual.