To perform a function; work: The motor operates smoothly. To perform surgery. To exert an influence: forces operating on the economy. To produce a desired or proper effect: a drug that operates quickly. To carry on a military or naval action or campaign. Informal To conduct business in an irregular or devious manner: drug dealers operating in residential and urban areas. To control the functioning of; run: operate a sewing machine. To conduct the affairs of; manage: operate a business.