From HomoExcelsior

1. A small space or interstice in a tissue or part, such as the area bounded by small veins in a leaf or the wing of an insect. 2. A small, specialized, cushionlike area on a cactus from which hairs, glochids, spines, branches, or flowers may arise. 3. A small ring of color around a center portion, as about the nipple of the breast or the part of the iris surrounding the pupil of the eye.

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