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.
In chemistry, a hydron is the general name for a cationic form of atomic hydrogen, represented with the symbol H+ . The term proton refers to the cation of protium, the most common isotope of hydrogen.nlike other ions, the hydron consists only of a bare atomic nucleus. The hydron (a completely free or naked hydrogen atomic nucleus) is too reactive to occur in many liquids, even though it is sometimes visualized to do so by students of chemistry.