Swinging Strike Rate
Swinging strikes, out of all pitches.
What it actually is. The share of all pitches, not just swings, that produced a swing and a miss.
What a scout reads off it. The older cousin of whiff rate and still the quickest sanity check on whether a strikeout total is real. Strikeouts without swinging strikes underneath them tend not to last.
Batter's Eye: look up anything in baseball