名词 trackball:

1. an electronic device consisting of a rotatable ball in a housing; used to position the cursor and move images on a computer screen

trackagen.轨道总称(铁路线全长)trackn.轨道；跑道；踪迹；小路；乐曲v.追踪；跟踪tracking generator跟踪发生器tracking behaviour跟踪行为tracking apparatus跟踪装置tracking regulator跟踪调节器tracking amplifier跟踪放大器track intersection航迹交叉track configuration磁迹位形track-idler wheel履带空转轮track laying gantry铺轨龙门架track cable scraper绳拉式耙矿机

1. Input devices include keyboards and pointing devices such as mouse,joystick,track ball, or light pen.
   输入设备包括键盘和点击设备如鼠标，操纵杆，跟踪球或光笔。