means An event where something almost went wrong — a collision, accident, or failure narrowly avoided — though logically it describes a miss that came close, not a hit.

from A straightforward English compound of "near" (close) and "miss" (a failure to hit), in use since at least the early 20th century and popularized by aviation, where pilots reported "near misses" of other aircraft. Pedants have long grumbled that a "near miss" should really be a "near hit," since the planes did in fact miss — but the phrase stuck, the logic be damned.