Not common; unusual; infrequent; rare; hence, remarkable; strange; as, an uncommon season; an uncommon degree of cold or heat; uncommon courage.
not common or ordinarily encountered; unusually great in amount or remarkable in character or kind; "uncommon birds"; "frost and floods are uncommon during these months"; "doing an uncommon amount of business"; "an uncommon liking for money"; "he owed his greatest debt to his mother's uncommon character and ability"
marked by an uncommon quality; especially superlative or extreme of its kind; "what is so rare as a day in June"-J.R.Lowell; "a rare skill"; "an uncommon sense of humor"; "she was kind to an uncommon degree"
To birders and ornithologists, a bird species which might be seen in a given locale at levels of no more than five birds daily; 5 to 25 times over the course of a season by an active observer. Somewhat less commonly occurring species are termed Rare.