What is the state of matter characterized by having a definite volume but no definite shape?

The state of matter that has a definite volume but no definite shape is classified as a liquid. In a liquid, particles are closely packed together, allowing for a fixed volume. However, the particles are not in fixed positions, which gives liquids the ability to flow and take the shape of their container. This characteristic distinguishes liquids from solids, which maintain both a definite shape and volume due to their tightly packed and organized particles.

In contrast, gases have neither a definite volume nor a definite shape; they expand to fill their container completely. Plasma, another state of matter, consists of ionized particles and can also fill a container without a defined shape or volume under normal conditions. Therefore, the properties unique to liquids make them the correct answer for this question.