Which word describes something that is easily bent or adaptable?

The term that describes something that is easily bent or adaptable is "pliant." This word is often used in both physical and metaphorical contexts. In a physical sense, pliant materials can easily change shape without breaking, such as rubber or flexible fabrics. In a metaphorical sense, pliant can refer to a person, organization, or system that is able to adjust to new conditions or requirements with ease.

In contrast, the other terms provided do not convey this sense of flexibility. "Outmoded" refers to something that is outdated or no longer in style, which does not imply adaptability. "Ponderous" describes something that is heavy, clumsy, or slow-moving, suggesting rigidity rather than flexibility. "Penitent" refers to a feeling of regret or remorse, which is unrelated to the capacity for bending or adaptability. Thus, "pliant" is the appropriate choice for describing something that can easily bend or adapt.