Here's why:

* Composition: Unlike the gas giants (Jupiter and Saturn) which are primarily composed of hydrogen and helium, Uranus and Neptune have a higher proportion of heavier elements, including ices such as water, methane, and ammonia.

* Structure: While still largely gaseous, ice giants have a distinct layer of ices beneath their atmosphere, forming a solid core.

* Appearance: Uranus and Neptune have a distinctive blue-green color due to the presence of methane in their atmospheres.

So, while Uranus is a giant planet, it's not a gas giant like Jupiter or Saturn. It falls into the category of ice giants due to its unique composition and structure.