开玩笑 (kāi wán xiào) is the standard verb phrase for to joke or to make a joke. 开 means to open or start, 玩 means play, and 笑 means to laugh. Together they describe the act of playing for laughs - making a joke. Common contexts: 我只是开玩笑 (I was just joking), 别开玩笑 (stop joking). The phrase 开个玩笑 (make a joke) is also very frequent. When used seriously it often clarifies or defuses a situation.