A session is a visit as an analytics product defines a visit. The usual cut is 30 minutes without another hit. Some products also cut at midnight or when the campaign tag changes. The web itself has no session. Two products can watch the same browser and disagree because they cut at different times.
Bounce rate is a property of sessions: the share that never produced a second tracked action. Without a session, that sentence has nothing to attach to. Pageview is the single hit a session may contain several of.
MapMyVisitors records widget loads and does not group them into sessions. Do not divide its counter by an imagined session length. If you need sittings, use a tool that builds them, and quote that tool's timeout. The longer version is what is a session.
