There are several synonyms for the term 'air-raid alarm', which is essentially a warning sound that is used to alert people of an impending air attack. The first synonym is 'civil defense siren', which is a common alarm used in many countries around the world. Another term that is often used is 'warning siren', which is more broader in its scope and can refer to any type of siren used for warning purposes. 'Emergency siren' is also a similar term that can be used interchangeably with 'air-raid alarm'. Finally, 'attack alarm' is a term that emphasizes the seriousness of the situation and is often used in military contexts.