bursa

1. Any of the many small fluid-filled sacs located at the point where a muscle or tendon slides across bone. These sacs serve to reduce friction between the two moving surfaces.
2. A diverticulum on the cloaca of young birds, which serves as a lymphatic organ and as part of the immune system, but which atrophies as the bird ages.
3. Any of various pouchlike organs for storing semen prior to copulation in the male or for receiving semen in the female.
4. A parament about twelve inches square in which the folded corporal is kept in for reasons of reverence.

Plural bursae