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. thyroid cartilage a large cartilage of the larynx, the projection of which in man forms the Adam's apple.
[ obs.F thyroide or mod.L thyroides, irreg. f. Gk thureoeides f. thureos oblong shield ]