1. A toroidal shape
   "The ring-shaped solar eclipse created an annulus around the moon";
   - ring, halo, doughnut, anchor ring
    
2. (Fungi) a remnant of the partial veil that in mature mushrooms surrounds the stem like a collar
   "The presence of an annulus helped identify the mushroom species";
   - skirt

Derived forms: annuluses, annuli

Type of: plant part, plant structure, toroid

Part of: partial veil

Encyclopedia: Annulus