Answer:
A liquid
Step-by-step explanation:
Liquids has an indefinite shape, which means it could change from one shape to another. For example, if you pour water into a rectangular fish tank. The shape of the liquid changes into a rectangle. Definite volume means its volume is consistent and that it is unchangeable. If you fill the rectangular fish tank with water, the volume of the water stays the same even though it changes shape.
Hope this helps.