I think calling it peer is misleading/imprecise, since in the context of the internet peer/peering refers to the interconnection of two networks, having your own AS, running BGP, etc.
That is what peering agreements are but I believe in the broader context of the Internet, any routable IP address can, and should be, considered a peer:
"Each layer has one or more protocols for communicating with its peer at the same layer."[1]
[1] TCP/IP Illustrated, Volume 1, p.3