A taxi operating without a medallion in New York is commonly called a gypsy cab.
In New York’s traditional system, a medallion is the city-issued authorization attached to a yellow taxicab. Medallion taxis are permitted to accept passengers who hail them on the street. Livery vehicles, by contrast, are generally supposed to pick up passengers through a prearranged booking rather than an unsolicited street hail.
When a livery or other non-medallion vehicle accepts street passengers outside the legal system, New York usage has traditionally called it a “gypsy cab.” The term is associated with unauthorized or illegal taxi operations, particularly in neighborhoods where official yellow cabs were less available. It describes the vehicle’s operating status, not a particular car model or paint color.
A common mix-up is treating “livery cab” and “gypsy cab” as synonyms. A livery cab can be legally licensed for-hire transportation; it becomes a gypsy cab when it performs unauthorized street pickups. Modern rules also recognize licensed street-hail livery, or green boro taxis, which are not gypsy cabs.