Longman Dictionary of Contemporary English - guard

~1 n 1 »PERSON« a) someone whose job is to guard a place, person, or object in order to protect them from attack or from thieves  (The guards stopped us at the gate.)  (- see also security guard) b) someone whose job is to guard prisoners and prevent them from escaping 2 be on guard to be responsible for guarding a place or person for a specific period of time  (Who was on guard when the fire broke out?) 3 keep/stand/mount guard (over) to guard a person or place  (Catherine kept guard over the horses while we looked for water.) 4 »GROUP« a group of people, especially soldiers, who guard someone or something. 5 be under (armed) guard to be guarded by a group of people with weapons 6 »THING« something that is fitted to a machine or worn on a part of your body to protect you against damage or injury  (a football player's mouth guard) 7 catch/throw/take sb off guard to surprise someone by doing or saying something that they are not ready to deal with  (Senator O'Hare was caught off guard by the reporter's question.) 8 be on your guard to pay careful attention to what is happening so that you avoid being tricked or getting into danger  (Be on your guard - they always try to cheat tourists. | lower your guard/let your guard down (=forget to be careful)) 9 »ON A TRAIN« BrE an official in charge of a train; conductor (4) AmE 10 »BOXING« the position of your hands in boxing when you are holding them up to defend yourself 11 the Guards special groups of soldiers in the British army whose original duty was to guard the king or queen ~2 v 1 to protect a person, place, or valuable object by staying near them and watching them  (The Sergeant told Swift to guard the entrance to the building. | guard sb/sth against)  (There is no one to guard these isolated farms against possible attack.) 2 to watch a prisoner and prevent them from escaping 3 guard your tongue old-fashioned used to tell someone to be careful of what they say so that they do not tell a secret guard against sth phr v to try to prevent something from happening by being careful  (Nurses should guard against becoming too emotionally attached to their patients.)