1. A bang path or explicitly routed Internet address; a node-by-node specification of a link between two machines. Though these are now obsolete as a form of addressing, they still show up in diagnostics and trace headers occasionally (e.g. in NNTP headers).
2. [Unix] A filename, fully specified relative to the root directory (as opposed to relative to the current directory; the latter is sometimes called a relative path). This is also called a pathname.
3. [Unix and MS-DOS/Windows] The search path, an environment variable specifying the directories in which the shell (COMMAND.COM, under MS-DOS) should look for commands. Other, similar constructs abound under Unix (for example, the C preprocessor has a search path it uses in looking for #include files).