An internal-combustion engine in which an explosive mixture is drawn into the cylinder on the first stroke and is compressed and ignited on the second stroke; work is done on the third stroke and the products of combustion are exhausted on the fourth stroke.

synonym: four-stroke internal-combustion engine.

Dutch: viertaktmotor
Polish: czterosuw, czterotakt, silnik czterosuwowy, silnik czterotaktowy