B1a person or group of people whose job is to protect a person, place, or thing from danger or attack, or to prevent a person such as a criminal from escaping: prison guardssecurity guardsThere are guards posted(= standing and watching) at every entrance.Armed guards are posted around the site.The frontier is patrolled by border guards.Protection and protectorsEnvironmental issuesbe under guard›to be kept in a place by a group of people who have weapons: The ex-president was under armed guard in the palace.Defending and protectingBacking, supporting and defendingPreserving and savingstand/keep guard(alsobe on guard)›to be responsible for protecting someone or something, or for preventing someone from escaping: Two of the soldiers kept guard over the captured guns.Armed police stand guard outside the house.Defending and protectingBacking, supporting and defendingPreserving and savingthe changing of the guard›a ceremony held outside Buckingham Palace in London when one set of soldiers replaces the soldiers who have finished their time on duty standing outside the palaceMilitary training and ceremonies