thyroid

adjective

1. designating or of a large ductless gland lying in front and on either side of the trachea and secreting the hormone thyroxine, which regulates body growth and metabolism: the malfunctioning or congenital absence of this gland can cause goiter, cretinism, etc.
2. designating or of the principal cartilage of the larynx, forming the Adam's apple

noun

1. the thyroid gland
2. the thyroid cartilage
3. an artery, nerve, etc. in the region of the thyroid
4. a preparation of the thyroid gland of certain animals, used in treating goiter, myxedema, etc.
   also thyroid extract