The word "flaccidities" refers to a state of being flabby, weak or lacking in firmness. The antonyms for this word include terms such as tautness, firmness, rigidity, strength, solidity, and muscularity. Tautness describes a state of being stretched or tight, the opposite of flabby. Firmness refers to a solid structure and can also refer to mental resolve. Rigidity means stiff and inflexible, while strength refers to something robust and sturdy. Finally, solidity refers to a state of being durable and unyielding, while muscularity refers to being toned and strong. These terms represent the opposite of flabbiness and weakness and can be used to describe physical objects, textures, or even personalities.