(Canada, US) A nickname for the approximately 1200-mile (1900-kilometer) portion of the border between Canada and the USA, extending along the forty-ninth parallel of latitude from Lake of the Woods to the Pacific Ocean.

(idiomatic, basketball) The NCAA strategy of playing a suffocating full-court press and aggressive offense for the entirety of a game.

(set theory) The paradox that supposing the existence of a set of all ordinal numbers leads to a contradiction; construed as meaning that it is not a properly defined set.

(Canada, US, idiomatic, obsolete) A very fast speed. / (Canada, US, slang, obsolete, by extension) The quality of being "fast", i.e. immoral in one's habits.