Holdup men are individuals who engage in criminal activities such as robbing or holding up people. However, there are several synonyms that can be used to describe such individuals. For instance, robbers are individuals who steal from people by using force or threats. Bandits are also individuals who engage in criminal activities such as robbery and kidnapping. Thieves are individuals who steal goods or items from people without their knowledge or consent. Burglars are individuals who enter into people's homes or offices to steal their valuables. Finally, hijackers are individuals who take control of vehicles, such as cars or airplanes, to commit crimes. These are just a few of the many synonyms that can be used to describe holdup men.