A 59' slider, 1.5' outside and in the dirt.
"A strike is any pitch the umpire calls a strike. The definition in the rulebook is merely a guide until baseballs adopts an electronic strike zone which is way overdue.."
It's like an error. The rules contain a definition, but the official scorer calls it an error or a hit.
The principles here are the ones taught to me as a fastpitch softball umpire, but everything transfers.
Imagine home plate as a pentagonal prism that extends upwards from the ground, a strike being from roughly the knees to the middle of the torso. If a ball enters that prism at any point, it is supposed to be called a strike.
Of course, in MLB it is not called this liberally - it is usually the top of the knees to the belt. So I defer to the person who said it is whatever the umpire calls as a strike. That is the simplest and most accurate definition however flawed it is.
"thanks, makes sense so, a pitch can bounce on the rear of the plate and still be a strike?"
This is an exception to my previous post. A pitch, in theory (an Ephus pitch), could go through the strike zone and land on the plate. However, by defintion of a strike (again, in softball, but I imagine it transfers) any pitch that hits the plate is a ball.