1. A programming device that lets you use the output of one process as the input of another. You must use a vertical bar (|) between two command invocations to indicate piping. From Linux Guide @FirstLinux

2. In DOS and UNIX a symbol that tells the operating system to send the output of one command to another command rather than display this output. In the following example, the pipe (represented by the | symbol) tells DOS tosend the output of the TREE command to the MORE command; the MORE command then displays the TREE result page by page on-screen: TREE C:\ | MORE See filter and input/output (I/O) redirection. From QUECID

3. n. [common] Idiomatically, one's connection to the Internet; in context, the expansion "bit pipe" is understood. A "fat pipe" is a line with T1 or higher capacity. A person with a 28.8 modem might be heard to complain "I need a bigger pipe". From Jargon Dictionary