1 [I,T] fasten sth (up) to close or join the two parts of sth; to become closed or joined 系；扣；关紧 · Please fasten your seat belts. 请系好安全带。Fasten your coat up -- it's cold outside. 把大衣扣上，外面很冷。My dress fastens at the back. 我的连衣裙是从背后扣上的。

2 [T] fasten sth (on/to sth);fasten A and B (together) to fix or tie sth to sth, or two things together 把（某物）系于某处；把（两物）系在一起: Fasten this badge on your jacket. 把这个徽章别在你的上衣上。How can I fasten these pieces of wood together? 我怎样才能把这些木头捆在一起？

3 [T] to close or lock sth firmly so that it will not open 紧紧关上或锁上: Close the window and fasten it securely. 把窗子关上，拴牢。