A water-ice planet (or water/ice planet) is a planet consisting entirely of water in the form of ice, i.e., with no silicate or iron core. It is a theoretical planet type, filling a spot in lists covering possible types of extra-solar planets according to density. Density can sometimes be estimated if stellar characteristics have been reasonably estimated and transits have revealed the planet's radius and radial velocity measurements have revealed its mass. Given the possibility that analysis of exoplanets might turn up a candidate with this density, naturally, possible formation processes and the stability of such planets has been explored.
The terms water and ice are employed with various meanings when used for theoretical planet types, so the intention may mean "made of this, through and through", or may refer to the core, or refer to the surface, or merely a significant part of the surface, e.g., speaking of Earth as a "water planet" or "ocean planet" since most of its surface is water. The surface material is typically used to coin the terms when albedo is the topic of discussion rather than density.