Apoplexy is uncontrolled bleeding into an organ. For example, adrenal apoplexy is bleeding into the adrenal glands, pituitary apoplexy is bleeding into the pituitary gland, and so on.
The term apoplexy (with no organ specified) often refers to bleeding into the brain. Conditions such as subarachnoid hemorrhage or stroke are sometimes called apoplexy.
Patel AJ, Fuller GN, Wildrick DM, Sawaya R. Pineal cyst apoplexy: case report and review of the literature. Neurosurgery. 2005; 57(5):E066.
Balarini Lima GA, Machado ED, Dos Santos Silva CM, Filho PN, Gadelha MR. Pituitary apoplexy during treatment of cystic macroprolactinomas with cabergoline. Pituitary. 2007 June 15 [e-pub].