.Stream.Term.Flush (gb.term)

Discards data written to the stream but not transmitted, or data received but not read, depending on the value of Mode:

Term.TCIFLUSH	Flushes data received but not read.
Term.TCOFLUSH	Flushes data written but not transmitted.
Term.TCIOFLUSH	Flushes both data received but not read, and data written but not transmitted.