1. Annulus (plural annuluses or Annuli) A ring- or donut-shaped area or structure

2. Annulus (plural Annuluses or annuli) A ring- or donut-shaped area or structure

3. Annulus [ ăn ′yə-ləs ] Plural annuluses Annuli (ăn′yə-lī′) A ringlike figure, part, structure, or marking, such as a growth ring on the scale of a fish.

4. Annulus [ ăn ′yə-ləs ] Plural annuluses Annuli (ăn′yə-lī′) A ringlike figure, part, structure, or marking, such as a growth ring on the scale of a fish.