To make something harder, stronger, or less easy to break or damage — or for it to become that way by itself. It works on physical things (toughened glass in a car window, leather that toughens with use) and, just as often, on people and rules. With people it means making someone able to bear hard things without being hurt: years of night shifts toughened her. With rules and laws it means making them stricter and harder to escape: the government wants to toughen the penalties for drunk driving. You will very often meet it with up — toughen up — which is mostly about a person's character, and is the phrase someone uses when telling you to stop complaining and be stronger. Careful there: "You need to toughen up" can be encouraging from a coach and quite unkind from a colleague, depending entirely on who says it. It is an everyday word, comfortable in the newspaper and in conversation alike.