Quotation from: Manual of Surgery

Written by: Alexander Miles and Alexis Thomson

_Necrosis_ is the term applied to the death of a tangible portion of
bone, and the dead portion when separated is called a _sequestrum_. The
term _exfoliation_ is sometimes employed to indicate the separation or
throwing off of a superficial sequestrum. The edges and deep surface of
the sequestrum present a serrated or worm-eaten appearance due to the
process of erosion by which the dead bone has been separated from the
living.