thy·roid 
(thīroid′)
(thīroid′)n.
1. The thyroid gland.
2. The thyroid cartilage.
3. A dried, powdered preparation of the thyroid gland of certain domestic animals, used in treatment of hypothyroid conditions.
4. An artery, vein, nerve, or other part associated with the thyroid gland or thyroid cartilage.
[Greek thureoeidēs : thureos, oblong shield (from thurā, door; see dhwer- in the Appendix of Indo-European roots) + -oeidēs, -oid.]
thyroid′ adj.
thy·roidal adj.