A sausage was a type of food, a meat product made of ground meat, and possibly other ingredients such as herbs and spices, usually packed into a tubular casing.
On Earth, Humans made sausages out of the meat of pigs (see also: pork, pork chop, pork rind, and bacon), although many other types existed.
Sliced segments of sausages were sometimes used in other foods, including as an occasional topping on pizza. Certain types of sausages were sometimes eaten in a bun, creating the snack dish known as hot dogs.
Philippa Georgiou likened the Control-possessed Leland to an "AI sausage", much to Nhan's disgust. (DIS: "Such Sweet Sorrow, Part 2")
Sausage was a popular food in New Berlin. (DS9: "The Maquis, Part I")
According to Doctor Phlox, sausage was one of Malcolm Reed's favorite foods. (ENT: "Silent Enemy")
On Deep Space 9, sausages made up part of the Chief's Special breakfast dish, the breakfast of choice of the day shift. (DS9: "The Assignment")
In 2374, a Golana-bound Miles O'Brien expressed his dismay at not finding any sausages in the picnic basket. (DS9: "Time's Orphan")
On Nepenthe, William T. Riker used the meat of a bunnicorn to make sausage. He even used it as one of the toppings for his family's pizza. (PIC: "Nepenthe")