Unbuffering

In data communications unbuffering occurs when the receiver must process each bit of data sent before the sender transmits the next bit of data. Buffering provides temporary storage (as a FIFO, first-in-first-out, buffer) of the received data so that the receiving processor can temporarily fall behind without losing data.

URLs:

High Performance Computing and Communications Glossary

This site has a wealth of definitions.

W3E References:

asynchronous

synchronous