The exact form called "紫乳鼎壶" is not a widely established, single canonical type in published catalogs, so the identification is somewhat ambiguous. Parsing the name helps: 紫 (zi) commonly refers to purple or to zisha (purple clay), 乳 (ru) suggests a nipple- or bud‑like projection or rounded bosses, 鼎 (ding) invokes the ancient tripod bronze vessel, and 壶 (hu) means teapot.

Taken together, a "紫乳鼎壶" would most likely be a zisha (purple‑clay) teapot that takes its silhouette from an archaic ding—a squat, sturdy body, possibly raised on short tripod feet or adopting the ding’s squat proportions—and decorated with one or more rounded, nipple‑like protuberances (乳) as a lid finial or shoulder ornament. Forms like this reflect a long Chinese tradition (especially strong from the late Ming into the Qing and in Yixing pottery) of recreating archaic bronze shapes in ceramic teapots for literati taste: solid, tactile vessels with simple, balanced lines suited to gongfu tea practice.

If you can share a photograph, I can give a more precise description of the construction, clay, surface finish and likely period or workshop.
Wood-fired handmade Yixing teapot made from Duanni clay sourced from the original Huanglongshan mine. Xu Shun Wei.