A pipeline is a series of pipes that liquid or gas flows through. A pipeline can also be a channel for other things, even ideas. The Internet is an information pipeline. No digging required!
While oil and natural gas often go through a pipeline, other substances are also transported this way, including water used for irrigation and even, in some cases, beer. You can use pipeline when you talk about other quick-moving things, like a source of goods, or even spoken communication. You could call the big companies in your city a kind of “job pipeline.” If you have an idea for a community pool in the pipeline, go ahead and hire the lifeguards!