Piping can refer to several related things:

1. A system of pipes that carries liquids or gases from one place to another. Buildings have piping for water, heating systems use piping to carry hot water or steam, and factories have piping networks that can stretch for miles. When a plumber installs new piping in a house, they're creating the hidden pathways that bring clean water in and carry wastewater out.
2. A thin cord or strip of fabric used as decoration on clothing, furniture, or cakes. You might see piping along the edges of a couch cushion or around the collar of a band uniform. Bakers use piping to create those decorative borders and flowers on birthday cakes, squeezing frosting through a bag with a special tip.
3. When something is piping hot, it means extremely hot, often steaming. Your grandmother might serve piping hot cocoa on a winter day, warning you to let it cool before taking a sip.

The word can also describe a high, shrill sound, like the piping of a piccolo or a bird's call.