To languish means to:

Languish describes a state of weakness or feebleness, particularly in the context of losing strength or vitality. It often conveys a sense of suffering from neglect or experiencing a decline in condition. This term is frequently used to express the idea of someone or something becoming inactive, weak, or failing to thrive, often as a result of adverse circumstances or lack of care.

In contrast, the other options depict positive growth or improvement, which does not align with the meaning of languish. For example, becoming stronger, flourishing, or reviving suggests an upward trajectory in health or vitality, opposing the essence of languishing. Therefore, the correct interpretation of languish aligns with the notion of becoming weak or feeble.