<p>In a installation of WebSphere Application Server with Network Deployment, a node is:</p>

<ol>
<li>a physical machine</li>
<li>an instance of operative system</li>
<li>a logical set of WAS instances that is independent of physical machine or OS instance</li>
</ol>

@ggasp Here is what I got off IBM's Information Center
A node is a logical grouping of managed servers.
A node usually corresponds to a logical or physical computer system with a distinct IP host address. Nodes cannot span multiple computers.
http://publib.boulder.ibm.com/infocenter/wasinfo/v6r1/index.jsp?topic=/com.ibm.websphere.nd.multiplatform.doc/info/ae/ae/cagt_node.html