Whiff:

A whiff is a missed shot or missed spray that should have connected, often because the player aimed poorly, reacted too late, or lost control of recoil. In Counter-Strike 2, the term is commonly used to describe an easy kill that was missed, especially in clutch situations or close-range duels. Players may say someone “whiffed” after failing to secure a kill despite having the advantage.

Related: Spray Control (Recoil Control), Crosshair Placement, Clutch (1vX)