noun one of the retractor muscles of the proboscis of certain worms.
2. retinaculum ·noun a connecting band; a fraenum; as, the retinacula of the ileocaecal and ileocolic valves.
3. retinaculum ·noun one of the annular ligaments which hold the tendons close to the bones at the larger joints, as at the wrist and ankle.
4. retinaculum ·noun 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.