What does volume means at the quantum level? 
The volume of the electron is the space bounds in which it is contained

says the @CuriousOne. But how can we define the volume in such a small range.
If we immerse a cuboid into a vessel full of water, then we can define its volume as the volume raised in the vessel.
Can you give an analogy to electron? Or any other better definition?
 A: The "volume in which it is contained" is an ill-defined notion for quantum objects.
Consider the simplest atom, the hydrogen atom, and look at the wavefunctions for the electron states. You find that, roughly,
$$ \psi(r) \propto \mathrm{e}^{-r}$$
so the probability to find an electron at a certain distance $r$ from the nucleus decreases with increasing distance, but never reaches quite zero.
The electron does not really occupy a "volume" as this shows, and neither does any other quantum object. We usually are satisfied with saying that a quantum object occupies a volume if the probability to find it outside it is "neglegible" - where how small it has to be to be neglegible depends on what you are looking for: For example, you might say that the nucleons of atoms are confined to the, well, nucleus, since you almost never find one of them outside - except for when you do, and that's called $\alpha$-decay.
A: When a cuboid is immersed in water, the molecules at each face of the cube repels the water molecules making the cuboid having a definite boundary and that causes it to have a definite volume. But, how do this analogy works with an electron?
     Hence, the volume at quantum level is indefinable.
