carrier pigeon
noun
1.
one of a breed of domestic pigeons having a large wattle around the base of the beak.
2.
a homing pigeon trained to carry messages.
Origin
1640-50
Examples from the web for
carrier pigeon
The nearest equivalent to tweeting, back then, was to send a message by
carrier pigeon
.
British Dictionary definitions for
carrier pigeon
carrier pigeon
noun
1.
any homing pigeon, esp one used for carrying messages