The phrase "liquid ocean" refers to a body of water that is in a liquid state, like the oceans we have on Earth. It means that the water is not frozen or vaporized, but instead is fluid and can flow. Full definition
Data taken by telescopes and other scientific instruments suggest that the moon has a massive liquid ocean under its surface. (techtimes.com)
That's why moons such as Jupiter's Europa and Saturn's Enceladus, among others, may be able to maintain liquid oceans beneath their... (sciencenews.org)
In our story on possible liquid oceans on Neptune's satellite Triton we... (newscientist.com)