Which term means lacking in amount or quality?

The term "meager" specifically refers to something that is deficient in quantity or quality. It conveys the idea of scarcity or inadequacy, suggesting that there is not enough of something to meet needs or expectations. In various contexts, such as food, resources, or even efforts, when something is described as meager, it points to a significant lack or underwhelming presence.

In contrast, the other terms present a more positive or abundant connotation. "Robust" suggests strength and vigor, "plentiful" indicates an abundance or a large quantity, and "generous" implies a willingness to give or share more than is usual. None of these terms reflect the idea of deficiency or insufficiency like "meager" does. Thus, "meager" is the most appropriate choice for describing something lacking in amount or quality.