noun
Mach; Mach number
Technical term for the ratio of speed to the speed of sound. Often used in compounds like マッハ数.
See also: マッハ数
この戦闘機はマッハ2で飛行できる。
This fighter jet can fly at Mach 2.
noun
at high speed; very fast
Colloquial use, often as マッハで, meaning 'at breakneck speed' or 'extremely quickly'. Not a precise measurement.
彼はマッハで宿題を終わらせた。
He finished his homework at lightning speed.