Liquid conforms to its container whether it is a glass, birdbath, or lake.
Liquid is differentiated from gases or vapors…
… as well as from solids.
Some molecules, like carbon dioxide, transform from solid to gas (or vice versa) usually with no intermediate liquid form. Liquid carbon dioxide can be produced with high pressure — above 5.1 atmospheres, about 75 psi.
Liquid doesn’t apply solely to fluids. Dancers can move with a liquid grace, people can have limpid, liquid eyes.
And let’s not forget those liquid assets. Though, in this household, they more closely resemble vapor.