For newbies: standover height defined

I'm shopping for a used bike and looking at lots of online ads. What do they mean when people write about the "stand over height" of a bike? The rider I'm shopping for is 5'10". —M

Standover height is the height of the bike at the top bar of the frame—better known as "the point where your crotch hits if you slip off the pedals." It's a measure not of whether the bike fits the rider, but of whether the rider can safely get on and off the bike. Your crotch-to-floor measurement in riding shoes really ought to be at least a couple inches taller than the bike's standover height.