- deficient activity of the thyroid gland
- the disorder resulting from this, characterized by a retarded rate of metabolism and resulting sluggishness, puffiness, etc.
- Insufficient production of thyroid hormones.
- Insufficient functioning of the thyroid gland.
Coined some time between 1900 and 1905 from the prefix "hypo-" (meaning "under), the word "thyroid," and the suffix "-ism" (meaning "a system of").