1 a person or an organization that buys something from a shop/store or business
one of the shop's best/biggest customers
They know me—I'm a regular customer.
the customer service department
The firm has excellent customer relations.
2 (old-fashioned, informal) used after an adjective to describe a particular type of person
an awkward customer
a cool customer (= somebody who is always calm, even when in trouble)
an ugly customer (= somebody who may become violent)