Not synchronised by a shared signal such as clock or semaphore, proceeding independently.Opposite: synchronous.1. A process in a multitasking system whose execution can proceed independently, "in the background".Other processes may be started before the asynchronous process has finished.2. A communications system in which data transmission may start at any time and is indicated by a start bit, e.g. EIA-232.A data byte (or other element defined by the protocol) ends with a stop bit.A continuous marking condition (identical to stop bits but not quantized in time), is then maintained until data resumes.(1995-12-08)