The antonyms for "firmness" can vary depending on the context in which the word is used. For instance, in terms of physical consistency, antonyms for firmness could include words like softness, sponginess, and pliability. However, if we are talking about a person's resolve or determination, the antonyms for firmness could include words like indecision, weakness, and wavering. In terms of behavior, antonyms for firmness could be passivity, leniency, and meekness. Therefore, the antonyms for "firmness" change depending on the situation and usage, making it an ambiguous word.