A warder is someone whose job is to guard prisoners in a prison. 'The warder unlocked the gate.' 'Two warders led him back to his cell.' The important thing is where the word lives. It is British, and it is somewhat old-fashioned. In Britain the official job title today is 'prison officer', and staff themselves prefer that, because 'warder' sounds like the Victorian era — keys on a belt, heavy doors, nothing but locking and unlocking. So you will find 'warder' in older novels, in newspapers reaching for atmosphere, and in prison memoirs, more than in a modern job advertisement. In American English the word is not really used at all; Americans say 'guard' or 'corrections officer'. A woman doing the job used to be called a 'wardress', but that word has gone out of use along with most feminine job endings. One more place you will meet it: the Yeomen Warders of the Tower of London, the guards in red and black uniforms that tourists photograph. They are nicknamed Beefeaters.

（英式、略舊）獄卒、監獄看守員；現在英國官方職稱是 prison officer，美式英文則說 guard