Broken Lance

Broken Lance is a private code used by Sentinel Prime and Optimus Prime in their academy days to indicate that Sentinel "was about to get caught doing something he shouldn't."

Fiction

Animated cartoon

When the Decepticons captured the Autobot flagship, Sentinel sent the codeword as an encrypted message "on an emergency sub-frequency" as a cry for help to Optimus. Decepticon Air

Notes

• "Broken Lance" is a derivative of the real-life U.S. military term "Broken Arrow" which is used to denote certain situations in which things go very wrong, specifically those involving nuclear weapons. Sentinel's "Lance" version is apparently used to describe more general cock-ups, specifically those involving himself.
• When viewed in the context of the episode in which it is used (which features no nuclear weapons, but does include the hijacking of a spaceship) the phrase is more likely to have been born out of a reference to the 1996 action film named after the real-life term in which John Travolta hijacks a stealth bomber in order to sell the nuclear missiles on board, which in reality would technically be classed as an "Empty Quiver" situation rather than a "Broken Arrow". Confused yet?
• "Lance", of course, refers to Sentinel's weapon of choice.