"Flag down" is a common term used to describe the act of stopping a vehicle, usually by standing on the side of the road and waving to get the driver's attention. However, there are several other synonyms for this phrase that can be used to convey the same meaning. Some examples include "hail," "stop," "catch the attention of," "call out to," and "signal for." These terms can be used interchangeably with "flag down" depending on the context in which they are used. So next time you need to stop a car, consider using one of these synonyms instead of the same old phrase.