Insolidity can be defined as the lack of firmness or stability, and there are several synonyms for this word. One synonym is instability, which refers to a state of being unsteady or unbalanced. Another synonym is fragility, which suggests a state of weakness or vulnerability. Brittle, flimsy, and precarious are other synonyms that convey a similar sense of weakness or insecurity. Meanwhile, malleability and flexibility suggest a lack of rigidity, but can imply adaptability or versatility. In all cases, synonyms for insolidity convey a sense of vulnerability or instability, whether it is physical, emotional, or intellectual.