noun: (anatomy) One of the annular ligaments which hold the tendons close to the bones at the larger joints, as at the wrist and ankle.
noun: (zoology) One of the retractor muscles of the proboscis of certain worms.
noun: (zoology) A loop on the underside of the forewing of some moths.
noun: (botany) A small gland or process to which bodies are attached; as, the glandular retinacula to which the pollinia of orchids are attached, or the hooks which support the seeds in many acanthaceous plants.