I guess by pocketable, I mean I fit the 7" tablet in my pockets for carrying, couldn't sit down comfortably though.

It will fit in my back jeans pocket, no worries about it falling out, in my work pants, I can fit it in the front pocket as well. Can't sit down without taking it out, but it does mean I don't need to carry a backpack/bag etc to take my tablet with me.

Pick it up, put it in a pocket and go, with a 10" tablet, you'd have to grab a bag or something, otherwise carry it in your hand, no way they'd fit in a pocket. Get where I'm going, pull it out, put it down somewhere safe (table, desk, car holder, etc).

Walking around, stop, pull it out of a pocket, use it, put it back. With a larger tablet, you'd have to open a bag, pull it out, re-arrange to use, re-arrange, put it back. Much simpler with a 7" tablet in your pocket. To me, simpler means more likely to use.

So, I guess to me, pocketable means it will physically fit in my pocket for transportation, but not that it would fit in my pocket and nobody would notice it there.