Wiktionary
t-minus
phr. (label en aerospace) (non-gloss definition: Usually specifies the remaining time until some future event (takeoff, encounter, et al.).)
Wikipedia
T-Minus (producer)
Tyler Williams (born February 25, 1988), professionally known as T-Minus, is a Canadian hip-hop and R&B producer from Ajax, Ontario. He has produced for artists such as Nicki Minaj, Beyoncé, Ciara, Drake, T.I., ASAP Rocky, Plies, LeToya Luckett, Birdman, Lil Wayne, Wale, August Rigo, Justin Bieber, Slaughterhouse and Ludacris among others. He won Top Producer at the 2012 BMI Urban Awards. He is also signed to Drake's OVO Sound with Noah "40" Shebib.
Usage examples of "t-minus".
At T-minus four minutes I recall hearing something about "Verify SSME valve movement in the close direction.