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)