courier

n. messenger

A courier is a person or company employed to deliver messages, packages and mail. Couriers are distinguished from ordinary mail services by features such as speed, security, tracking, signature, specialization and individualization of services, and committed delivery times, which are optional for most everyday mail services. As a premium service, couriers are usually more expensive than usual mail services, and their use is typically restricted to packages where one or more of these features are considered important enough to warrant the cost.
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Noun
1. a person who carries a message
(synonym) messenger
(hypernym) traveler, traveller
(hyponym) conveyer, conveyor

(n.)
An attendant on travelers, whose business it is to make arrangements for their convenience at hotels and on the way.
  

(n.)
A messenger sent with haste to convey letters or dispatches, usually on public business.
  

An individual, usually a representative of an object or document owner or a repository, who travels with an item to ensure its proper care and safe arrival at a venue.