If there is an axis of "commonness" upon which things can be measured, with "never happens" on the left side, and "always happens" on the right side, then "unco

If there is an axis of "commonness" upon which things can be measured, with "never happens" on the left side, and "always happens" on the right side, then "uncommon" would be a small section on the left, and "common" would be a small section on the right; everything between these sections could be "not uncommon."