parathyroid Syllabification: (par·a·thy·roid)Pronunciation: /ˌparəˈTHīˌroid/Definition of parathyroid noun Anatomy a gland next to the thyroid that secretes a hormone ( parathyroid hormone) that regulates calcium levels in a person’s body. parathyroid in other Oxford dictionaries Definition of parathyroid in the British & World English dictionary