a group of soldiers ceremonially welcoming an important visitor
仪仗队
act as a guard
站岗，放哨
unprepared for some surprise or difficulty
猝不及防，丧失警惕
the government was caught off guard by the unexpected announcement.
政府被这突如其来的声明弄得措手不及。
on duty to protect or defend something
站岗，放哨；值班
adopt a defensive posture
摆出防御姿势
(Cricket)(of a batsman) stand in position ready to receive the ball, especially having asked the umpire to check the position of one's bat with respect to the stumps
(板球)（击球员）站到正确的击球位置
being guarded
在看守下，在警卫下
he was held in an empty stable under guard.
他被关在一个有警卫看守的空马厩里。
Not alert; unprepared.
不警觉的；未准备的
Alert and watchful; cautious.
谨慎的：警觉且戒备的；谨慎的
To keep watch.
监视，守望
To act as a sentinel.
担当哨兵的工作