The phrase "drop a dime" has its roots in the late 20th century, when a payphone call required a dime to connect. It means to make an anonymous phone call to report a crime or wrongdoing. There are several synonyms for this phrase, such as "make a report," "rat someone out," "blow the whistle," "snitch," "tell on someone," "turn someone in," or "inform on someone." While "drop a dime" has a somewhat nostalgic connotation, the others may have negative connotations for those who don't view informing on others positively. However, ultimately, the synonyms indicate an act of reporting an offense to the authorities or others who can help.