There are compulsions, and then there are compulsive behaviours. The purpose of an OCD compulsion is to ward off anxiety. Compulsive behaviours on the other hand, are motivated by the need or desire (you choose) for gratification. In practice, the difference between the two can feel subtle, or even non-existent.
Skin-picking, which I discussed a few posts back, is one example of a behaviour which can become compulsive. Other relatively common ones include gambling, internet use, sexual behaviour, eating and shopping.
I've been thinking about shopping lately. My mother died a couple of months ago, and I'm in the process of clearing out her flat. She had quite an impressive shopping habit, and every shelf, cupboard, drawer and basket in the place is packed with the evidence: coats, tops, trousers, occasion wear, scarves, bargains with the tags still on, purses, handbags and luggage. An impressive collection of luggage: before she got ill, my mother went on a lot of trips, and there was always some reason or other why the luggage she had already wasn't quite suitable for the climate, terrain, journey or length of stay this time around. Ditto her clothing. I know this because my mother always needed to justify her purchases aloud: she was, like me, a reassurance-seeker.