Meaning
To signal a vehicle to stop by waving your arm.
Example Sentence
"I managed to flag down a taxi just as it started to pour."
Synonyms
hail
wave down
stop
Usage Note
This phrasal verb is separable. When using a noun object, it can go between the verb and particle or after the particle. When using a pronoun object, it must go between the verb and particle (e.g., "turn it off" not "turn off it").