sheep-dogging

The act of someone you are walking with failing to move laterally with you to allow you to pass obstacles. Instead, you are forced to slow down and follow them until you pass the obstacle, and then pick up the pace to catch up to your oblivious walking mate. You could also speed up to pass the obstacle first and let him/her catch up to you as well, but unfortunately this usually does not occur because you normally will have given your walking mate the benefit of the doubt prior, and up and to, the point of no return.