canary

A small, usually yellow, finch (genus Serinus), a songbird native to the Canary Islands.

Any of various small birds of different countries, most of which are largely yellow in colour.

A female singer, soprano, a coloratura singer.

An informer or snitch; a squealer.

A light, slightly greenish, yellow colour.

A (usually yellow) capsule of the short-acting barbiturate pentobarbital/pentobarbitone (nembutal).

A yellow sticker applied by the police to a vehicle to indicate it is unroadworthy.

Any test subject, especially an inadvertent or unwilling one. (From the mining practice of using canaries to detect dangerous gases.)

A value placed in memory such that it will be the first data corrupted by a buffer overflow, allowing the program to identify and recover from it.

A change that is tested by being rolled out first to a subset of machines or users before rolling out to all.