n.哨兵；传送器；[计]标记符号
v.放哨；设岗哨
The sentinel was stationed on a hill. 哨兵被派在山上站岗。
The press is a sentinel of our liberty. 新闻界是捍卫我们自由的卫兵。
At either end of the bridge a sentinel stood with rifle at ready. 桥的两头各有一名哨兵，荷枪实弹守卫着。
