Unsolid is a word used to describe something that lacks stability or firmness. Other synonyms for this word include unstable, wobbly, shaky, rickety, and precarious. These words all suggest a similar sense of uncertainty or insecurity. When describing physical objects such as furniture or structures, terms like flimsy, fragile, or delicate may also come to mind. In a more abstract sense, the words unreliable or inconsistent may be used to describe something that is unsolid. Overall, there are many different words that can be used to convey the same or similar meaning as unsolid, each with their own connotations and nuances.