A Starfleet code phrase by which a landing party tells its ship that it is in trouble but that no action is to be taken to rescue it.
Condition green is a code used by Starfleet landing parties in the original series. Spoken as if it were an all-clear, it in fact tells the ship that the party is in trouble and at the same time forbids the ship to do anything about it.
It is used in Bread and Circuses. Captured on planet 892-IV, a world like a twentieth-century Rome, Kirk is made to contact the Enterprise by the proconsul Claudius Marcus, who wants the crew brought down. Kirk tells Scott only that the situation is condition green.
Scott understands at once and keeps to the letter of the order, since the Prime Directive rules out a show of force. He instead blacks out the city's power for a moment from orbit, a harmless reminder that gives Kirk the chance he needs to escape.