*switch² n [C] 1 the part that you press up or down on a machine, light etc so that it starts or stops operating 〔机器、电灯等的〕开关，电闸: a light switch 电灯开关 2 a change from doing or using one thing to doing or using something else 转换; 改做; 改用: The switch to the new computer system has been difficult. 改用新的电脑系统并非易事。