Merriam-Webster's Collegiate® Dictionary, 11th Edition
JAW
I. noun
Etymology: Middle English
Date: 14th century
1. either of two complex cartilaginous or bony structures in most vertebrates that border the mouth, support the soft parts enclosing it, usually bear teeth on their oral margin, and are an upper that is more or less firmly fused with the skull and a lower that is hinged, movable, and articulated with the temporal bone of either side, the parts constituting the walls of the mouth and serving to open and close it, any of various organs of invertebrates that perform the function of the vertebrate jaws, something resembling the jaw of an animal: as, one of the sides of a narrow pass or channel, either of two or more opposable parts that open and close for holding or crushing something between them,
3. a space lying between or as if between open jaws , a position or situation in which one is threatened , a friendly chat,
II. verb
Date: 1748
intransitive verb to talk especially abusively, indignantly, or long-windedly , transitive verb to talk to in a scolding or boring manner