Определение t minus в Английский Язык Английский Язык словарь
This comes from a countdown convention used in by both the American military and NASA. Generally, it is used when counting down to a major event that will happen at a specific time. Mathematically, T is time, minus whatever amount of time is left until the event happens. If the News Years ball is dropping in 10 minutes, one could say "The ball is dropping in T minus 10 minutes and counting!"