Definition: A Selective Peering Policy is an articulation of an inclination to peer, but with some conditions.
These networks may peer with networks that meet reasonable and reachable criteria. This definition is a little slippery as some might argue that their "restrictive" peering policy is reachable by those that matter and that they are therefore "selective" not "restrictive." This is why we also have a peering inclination. The behavior which more closely resembles the peering inclination is what you need to look at to determine whether a peer is selective or restrictive.