What is "cross pattee"

n. Any of several forms of cross whose arms are narrow at the center and broad at the extremities

A cross pattée (or "cross patty", known also as "cross formée/formy") is a type of cross which has arms narrow at the center, and often flared in a curve or straight line shape, to be broader at the perimeter. The form appears very early in medieval art, for example in a metalwork treasure binding given to Monza Cathedral by Queen Theodelinda (d. 628), and the 8th century lower cover of the Lindau Gospels in the Morgan Library. An early English example from the start of the age of heraldry proper (i.e. about 1200) is found in the arms of Baron Berkeley.