Answer: NOUN: When I went to New York, I had to whistle to get a taxi to ride back to my hotel.
VERB: After an hour delay, our plane taxied to the runway for takeoff.
ADJECTIVE: I ran to the taxi stand to get a cab to the airport.
INTERJECTION: Taxi!
Explanation: For the interjection (it's kinda lame) you can just use the one word.