guard
noun
ɡɑːd 
ɡɑːrd people who protect
1 [countable] a person, such as a soldier, a police officer or a prison officer, who protects a place or people, or prevents prisoners from escapinga security guardborder guard sThe prisoner slipped past the guards on the gate and escaped.A guard was posted outside the building. compare warder see also bodyguard, coastguard, lifeguard2 [countable + singular or plural verb] a group of people, such as soldiers or police officers, who protect somebody/somethingthe captain of the guardthe changing of the guard (= when one group replaces another)The guard is/are being inspected today.Fellow airmen provided a guard of honour at his wedding.The President always travels with an armed guard. see also National Guard, old guard, rearguard3 [uncountable] the act or duty of protecting property, places or people from attack or danger; the act or duty of preventing prisoners from escapinga sentry on guard (= at his or her post, on duty)to do guard dutyThe escaped prisoner was brought back under armed guard.The terrorist was kept under police guard.One of the men kept guard, while the other broke into the house.4 the Guards [plural] (in Britain and some other countries) special regiments of soldiers whose original duty was to protect the king or queenthe Scots Guardsa Guards officeragainst injury
5 [countable] (often in compounds) something that covers a part of a person's body or a dangerous part of a machine to prevent injuryEnsure the guard is in place before operating the machine. see also fireguard, mouthguard, mudguard, safeguard, shin guardin boxing/fencing
7 [uncountable] a position you take to defend yourself, especially in a sport such as boxing or fencingto drop/keep up your guard (figurative) In spite of the awkward questions the minister never let his guard fall for a moment.in basketball
8 [countable] one of the two players on a basketball team who are mainly responsible for staying close to opposing players to stop them from scoringin American football
9 [countable] one of the two players on an American football team who play either side of the centre forwardIdioms
be on your guard
to be very careful and prepared for something difficult or dangerous
mount/stand/keep guard (over somebody/something)
to watch or protect somebody/something
Four soldiers stood guard over the coffin.off (your) guard
not careful or prepared for something difficult or dangerous
The lawyer's apparently innocent question was designed to catch the witness off (his) guard.