This is an unconscious masculine reflex to observe, and/or admire a random woman's curvy ass while in the company of your spouse, or significant other.
My buddy James is temporarily living in my crib as a result of an ass'ccident that occured yesterday while shopping at the mall with his girlfriend.
When you are observing an attractive person (of either sex), and usually, but not necessarily their ass, and you become distracted enough that you run into something, either in your car or while walking.
I saw this really hot girl doing squats at Taylor gym, and I almost got into an assccident while walking up the stairs.