A bt cannon is an opener/strategy in tetris, which is a tsd followed up by a tst, then a c spin, then possibly a perfect clear end. While not as useful in versus games, it is definitely op in blitz/ultra mode

n. The birth name of somebody who has changed their name. Most commonly attributed to trans people, but can be attributed to any person who has changed their name. (sometimes written as two words: dead name)

v. 1. To call somebody by their deadname.
v. 2. To out somebody's deadname to the public.