Final answer:
The brevity code word indicating 'last transmission potentially disclosed unauthorized information' is 'BEADWINDOW.' It is used in military radio communications to highlight a security breach.
Step-by-step explanation:
The brevity code word that means 'last transmission potentially disclosed unauthorized information' is 'BEADWINDOW'.
This code word is used in radio communications, especially in military contexts, to indicate that a speaker has just said something that should not have been transmitted over an insecure network, potentially compromising sensitive or classified information.
When 'BEADWINDOW' is used, the person who made the original statement knows to cease talking about sensitive topics and a report will typically be generated to assess the potential impact of the disclosure.