If you describe something as uncommon, you mean that it does not happen often or is not often seen.
Cancer of the breast in young women is uncommon...
A 15-year lifespan is not uncommon for a dog.
If you describe a quality, usually a good quality, as uncommon, you mean that it is unusually great in degree or amount.
Both are blessed with uncommon ability to fix things...
She read Cecelia's last letter with uncommon interest.
Such attitudes were not at all uncommon thirty years ago.
It is not uncommon that a sunny morning will turn out to be a cloudy day at this time of the year.
Phil has uncommon intelligence.
Even if the boy is of uncommon brilliance,he should not have been praised to the skies.
There was an uncommon likeness between the two boys.