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.
Fn is simply a modifier to allow the same key to be used for two purposes. It started on laptop keyboards, where space was at a premium, and has since migrated to Apple's regular keyboards.