someone whose job is to protect a place or person:
There were two security guards on duty outside the building.
We were stopped by border guards.
Armed guards were posted by the exit.
someone whose job is to prevent prisoners from escaping:
The prison guards were reasonably friendly.
the act or duty of protecting places or people, or of preventing prisoners from escaping
be on guard
Who was on guard the night the fire broke out?
keep/stand guard (over somebody/something)
Gunmen stood guard at the camp entrance.
be under (police/armed etc) guard (=to be guarded by a group of people)
He was taken to hospital, where he is now under police guard.
a group of soldiers who guard someone or something:
The President has called in the National Guard.
b) British English
a group of soldiers who protect the king or queen
something that is used to protect someone or something from damage or injury:
a face guard
a fire guard
a person whose job is to be in charge of a train [= conductor American English]
on a train[countable] British EnglishBOTTT
to be paying attention to what is happening in order to avoid danger, being tricked etc:
These men are dangerous so you'll need to be on your guard.
Something in his tone put her on her guard.
to surprise someone by doing something that they are not ready to deal with:
Senator O'Hare was caught off guard by the question.
a group of people who walk or stand together at a special occasion in order to show respect:
Police colleagues formed a guard of honour at her funeral.
a group of people in an organization who want to do things in the way they were done in the past:
the Communist old guard
the position of holding your arms or hands up in a fight in order to defend yourself:
He swung at me and I brought my guard up.
one of two players on a basketball team who is responsible for moving the ball to help their team gain points
one of two players on an American football team who plays either side of the centre