[greymule]

This can be traced to a point in the early 1960s, when a "one-second stop" was instituted. Naturally, many balks followed, so MLB changed it to just a "stop." Since hands coming together and reversing direction had technically stopped at some point, pitchers (like me) loved simply to change direction.

To deal with that "loophole," MLB followed with what SanDiegoSteve described earlier, the "complete and discernible stop" and then just the "complete stop."

When I pitched (1963-1972), you had to do something outrageous to be called for a balk. No technicalities.

Something else I remember from the late 1960s: there was some violation a pitcher could commit that caused a ball, not a balk, to be called, and one of our (college) pitchers tried to walk a batter intentionally by committing that violation four times. However, he wasn't doing the violation "correctly" and, provoking no call, would step back off the plate and start again, trying to be more obvious about his violation. I was playing infield, and after the pitcher did this a few times, the BU asked me, "What's he doing?" I said, "He's trying to get a ball called, but he's balking instead." The BU took another look and said, "You're right. That is a balk." So I asked for time, went to the mound, and told the guy to give the intentional walk in the regular way. (I'm not sure; whatever rule that was might have been college only.)