Other forms: lemniscates
If a mathematician uses the word lemniscate, they're just using fancy math jargon to mean "shape of a sideways figure eight."
When you write out the number eight and turn it on its side like an infinity symbol, it's a lemniscate. Mathematicians use the word for algebraic curves that take that exact shape, two symmetrical loops meeting at a center point. If you imagine a length of string in the form of a sideways 8, it makes sense that lemniscate comes from the Late Latin lemniscus, "a ribbon" and its Greek root lēmniskos, "a woolen ribbon."