The Collaborative International Dictionary
taxicab \tax"i*cab\, n. an automobile with a professional driver which can be hired to carry passengers; -- also called a taxi, and informally called a cab or a hack. The driver of a taxicab is referred to as a cab driver or cabbie, and sometimes as a chauffeur or hackie.
Note: Taxicabs may be engaged by a prior appointment made, e.g. by telephone, or they may cruise for passengers, i.e. they may drive in city streets and stop to pick up pasengers when they are signalled by a prospective passenger. The act of signalling a taxicab (usually by a wave of the arm) is often called
Usage examples of "to flag down a cab".
My mind made up, I drove the Olds to the outskirts of a slum area, left it there, and tried to flag down a cab.
Dressed as they were, they had been unable to flag down a cab in the Upper West Side, and had been forced to take the subway.
My only chance was to make it to the street, to flag down a cab, somehow beg a ride from a passing car, or maybe get some help.