customer

noun

1. (obsolete)A habitual patron, regular purchaser, returning client; a person or company who has a custom of buying from a particular business.
2. A patron, a client; a person or company who purchases or receives a product or service from a business or merchant, or intends to do so.

   “Every person who passes by is a potential customer.”

   “Airlines are the chief customers of the commercial divisions of large-aircraft manufacturers such as Airbus, Boeing, and Embraer.”

3. (informal)A person, especially one engaging in some sort of interaction with others.

   “a cool customer, a tough customer, an ugly customer”

   “Pug could just see Slote's pale face under his fur hat. "I don't agree with you on that. He's a pretty tough customer, Hopkins."”

   “This switch led to Philip Hammond becoming the Transport Secretary and he quickly proved to be a tricky customer, asking questions about rail spending and reining it back whenever possible.”

4. (India, historical)A native official who exacted customs duties.

   “His houses […] are seized on by the Customer.”

   “The Customer should come and visit them.”

   “The several affronts, insolences, and abuses dayly put upon us by Boolchund, our chief Customer”