It is basically another word for bow-legged. It is where the hocks turn out. The opposite of cow-hocked.
But, like I said, it is kinda hard to tell with the angle of the pic. If he is, it is only slight. Or, he could just be a little base narrow on the back.
Nothing bad, just a slight appearance issue, most horses have at least 1. Still a stunner.
Here is a picture. <Bow-legged Base Narrow>
Lovely pictures. However, in order to really see your horse, put up a absolute side view with the horse standing square (the ones you have are at an angle, just step back and take the picture straight on the side). It's hard to evaluate a horse when the angles are all skewed in the picture :)
Gotta say though, I am jealous of those braids! Mine never come out so nice :)
Hah thank you!! He is a bit base narrow, but it doesnt seem to affect his performance.. these were taking at a very small show around 2 years ago, so it was hard for mum to take good confo pictures haha but i'll get some updated ones =) and the braids look much better when sewn in, I didnt know how to do it then haha