On Friday my teacher was trying to explain coupé derriere to someone who wasn't quite getting it. Because in front you are wrapping your foot around your leg, right? But in back you are angling your foot out all weird. So I said "pretend you are wrapping your foot around someone else's leg back there" and that seemed to do the trick. Teacher was impressed by the description, but honestly I only know what I am talking about because my first ballet teacher, a million years ago, was a very cute young man, and he stood directly behind me and told me to wrap my foot around his leg.
You don't forget that.