|an arrangement of five objects, as trees, in a square or rectangle, one at each corner and one in the middle.|
|the offspring of a zebra and a donkey.|
periosteum per·i·os·te·um (pěr'ē-ŏs'tē-əm)
n. pl. per·i·os·te·a (-tē-ə)
The thick fibrous membrane covering the entire surface of a bone except its articular cartilage and serving as an attachment for muscles and tendons.