guard
noun [ C ]
uk/ɡɑːd/ us WORKPLACE
a piece of equipment that protects the user of a machine from being injured by a sharp or dangerous part on the machine:
Make sure that the safety guard is in position before using the cutting machine.
a person or group of people whose job is to protect a person, place or thing, or to prevent a person, such as a criminal, from escaping:
a night guard at a bank
border/prison/security guards
be on your guard (against sth)
to be careful to avoid being tricked or getting into a dangerous situation:
Stores must always be on their guard against credit card fraud.
guard
verb [ I or T ]
uk/ɡɑːd/ usto protect something from being known, found, harmed, or taken:
The California-based company is aggressively guarding its secret technology.
guard (sth) against sth The firewall guards the computer against viruses or other harmful programs.