Summary: Merriam-Webster's Word of the Day for April 24, 2013 is: occlusion \uh-KLOO-zhun\ noun 1 : a shutting off or obstruction of something 2 : the coming together of the surfaces of the upper and lower teeth 3 : the front formed by a cold front overtaking a warm front and lifting the warm air above the earth's surface Examples: Heart attacks result from the occlusion of blood supply to a part of the heart. "Three days before Thanksgiving 2011, Marilyn Mathern experienced a small blood clot, or retinal occlusion, in her eye." From an article by Briana Wipf in the Great Falls Tribune (Montana), February 26, 2013 Did you know? "Occlusion" is a descendant of the Latin verb "occludere," meaning "to close up." "Occludere" in turn comes from the prefix "ob-," here meaning "in the way," and the verb "claudere," meaning "to close or shut." "Occlusion" is one of many English terms derived from "claudere." Some others are "recluse," "seclusion," and "exclude." An occlusion occurs when something has been closed up or blocked off. Almost all heart attacks are the result of the occlusion of a coronary (heart) artery by a blood clot. When a person's upper and lower teeth form a "malocclusion," they close incorrectly or badly. An occlusion, or occluded front, happens when a fast-moving cold front overtakes a slow-moving warm front and slides underneath it, lifting the warm air and blocking its movement.
