IPA: //ʌnˈkʌmənər//
KK: /ʌnˈkʌmənər/
Referring to something that is less common or more rare than usual.
The uncommoner species of birds are often harder to spot in the wild.
Comparative: uncommoner
Superlative: uncommonest
Uncommoner → It is formed from "un-" (meaning not) and "common" (from Old French *comun*, meaning shared or belonging to all) and the suffix "-er" (meaning a person who). The word "uncommoner" refers to a person who is not common or ordinary.
Think of someone who is 'not' ('un-') 'shared' or 'ordinary' ('common') — that's why an uncommoner is someone who stands out from the crowd.