The Maximum Receive Unit is sent to inform the peer that the implementation can receive larger packets, or to request that the peer send smaller packets.

Maximum Receive Unit. Sets the maximum size of the information field within a packet.

See Maximum Receive Unit (MRU).

Mano River Union

This isn't as much of an actual term, as it is a frequently-seen acronym in the Registry. It stands for Most Recently Used, and is generally used in conjunction with lists of stuff you've recently typed in. For example, there's an MRU list for the things you've most recently typed into the Start Menu's Run command.