Used to label an unusually large number of occurrances of a disease or condition in one place. An autism cluster would be an unusually large number of cases of autism in (perhaps) a single locality. Clusters constitute evidence in the search for causes of diseases and conditions.
Top definition. jawn. a word used by Philly cats to describe anything and everything. NY cats interject with the word joint but it doesn't convey the same feelings.
Definition of leaven. 1  1a : a substance (such as yeast) used to produce fermentation in dough or a liquid; especially : sourdoughb : a material (such as baking powder) used to produce a gas that lightens dough or batter. 2  2 : something that modifies or lightens.