Shaped like an oblong shield; shield-shaped; as, the thyroid cartilage. [1913 Webster]
Of or pertaining to the thyroid body, thyroid cartilage, or thyroid artery; thyroideal. [1913 Webster]

Thyroid cartilage. See under Larynx. -- Thyroid body, or Thyroid gland (Anat.), an endocrine gland having two lobes, located in the floor of the mouth or the region of the larynx, which secretes two hormones (thyroxine and triiodothyronine) that regulate the rates of growth and metabloism. In man and most mammals it is a highly vascular organ, partly surrounding the base of the larynx and the upper part of the trachea. Cases of hypothyroidism, where the gland is insufficiently active, can be treated by administration of thyroxine or a combination of thyroxine and triiodothyronine. -- Thyroid dislocation (Surg.), dislocation of the thigh bone into the thyroid foramen. -- Thyroid foramen, the obturator foramen.

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OXFORD DICTIONARY

thyroid, n. & adj.
--n. (in full thyroid gland)
1 a large ductless gland in the neck of vertebrates secreting a hormone which regulates growth and development through the rate of metabolism.
2 an extract prepared from the thyroid gland of animals and used in treating goitre and cretinism etc.
--adj. Anat. & Zool.
1 connected with the thyroid cartilage (thyroid artery).
2 shield-shaped.

Idiom

thyroid cartilage a large cartilage of the larynx, the projection of which in man forms the Adam's apple.

Etymology

obs.F thyroide or mod.L thyroides, irreg. f. Gk thureoeides f. thureos oblong shield

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