DATAGRAM
A self-contained, independent entity of data carrying sufficient information to be routed from the source to the destination computer without reliance on earlier exchanges between this source and destination computer and the transporting network. See also: frame, packet. [Source: J. Postel]
In TCP/IP networks ,datagram is a synonym for packet.
A formatted set of electronic data used in communication between computer systems. Datagrams consist of two parts: the data proper (which may be part of a longer message), and the header (which indicates the source, the destination, and the type of data).