What is the scientific word that defines Solid but Unstable?

Question

I believe it starts with the letter "Q".

And an example of what I am writing about is, when a ice cube is solid, but it is unstable because it can melt. And the flip side is, when the ice cube melts, it is no longer solid, but it is now stable.

Another example, is a clean bedroom, solid when clean, but unstable, because it can get messy. When messy, not solid, but stable.

Answer 1

It doesn't meet your standard, but perhaps you are thinking of a quasistatic equilibrium in thermodynamics, or a quasistable equilibrium (saddle point) in mechanics.

Answer 2

Jello

Answer 3

volatile?