line of fire

WordReference Random House Unabridged Dictionary of American English © 2025

line′ of fire′, 

1. Military the straight horizontal line from the muzzle of a weapon in the direction of the axis of the bore, just prior to firing.

• 1855–60

Collins Concise English Dictionary © HarperCollins Publishers::

line of fire noun

1. the flight path of a missile discharged or to be discharged from a firearm