Retirement

[Sonia]

The act of retiring, or the state of being retired;
withdrawal; seclusion; as, the retirement of an officer.

[Jason Yan]

throwing away a machine or human after it is decided that they are so worn out or used up that there is no value left. the human gets a small pension that is not enough to live on, the machine is junked.

[Raeanne Dimick]

A myth. Something hard working people look forward to all their working lives, only to be disappointed by the fact that they cant afford to live off there substantially small pensions for the rest of their lives.

[Luis Fok]

Retirement is when a robot that strongly resembles a human is killed. Because humans do not consider robots to be alive in the first place, killing a robotic servant of mankind is seen as retiring a machine and not murder.
The term originated in the openning scrawl of the science fiction film masterpiece, Blade Runner, desribing what Blade Runners do to Replicants (robots so advanced they are indestinguishable from humans):
Special police squads - BLADE RUNNER UNITS - had orders to shoot to kill, upon detection, any trespassing Replicant.
This was not called execution. It was called retirement.
Loosely, the is often used in scifi circles to refer to any instance when a (usually) humanoid robot that is designed to look human is terminated by a human, such as on the 2004 Battlestar Galactica with the new humanoid Cylons (the new Cylon models are very similar to Replicants, and Edward James Olmos appears in both Blade Runner and BSG).

[Little_Girl]

The action or fact of leaving one

[Ernesto]

A [phase] in your life when you can afford the good things in life but can’t quite enjoy them—when your [health] and your [wealth] decide to part ways.