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] 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).