courier-n; 3 Senses

Sense Number 1: a transporter of information (messenger) and/or goods

Commentary: COURIER[+person][+transporter][+information][+messenger][+diplomatic/+espionage] [+goods][+military/+contraband]
NOTE: references a person, not an organization

Sally worked as a courier on a bicycle in New York City.
The medication was hand-delivered by courier at 3 AM. (a person dropped it off)
He served as a courier to the American Embassy in Kenya.
The novel is about a double agent during the Cold War who was a courier for the KGB.
The drug cartels have couriers on commercial flights transporting cocaine.
Army couriers risked their lives delivering medicines and other supplies to the front.

WordNet 3.0 Sense Numbers: 1

Sense Number 2: a business that transports small parcels, e.g., documents

Commentary: COURIER[+organization][+business][+transporter][+parcel][+small][+document/+medicine]
NOTE: references a business, not a person

That firm is an overnight courier of documents and small packages.
Packages transported by companies that qualify as trusted couriers are not inspected.

WordNet 0.0 Sense Numbers: 1a

Sense Number 3: a paid tour guide

Commentary: COURIER[+person][+guide][+tour]

The courier waited by the bus while the tourists explored the shops.
Our Italian courier pointed out interesting architectural details at Pompeii.

WordNet 0.0 Sense Numbers: 2