The word inspissated means something that is thickened or thickened up, and its antonyms refer to things that are thin, rare, or pure. The opposite of most inspissated would be something that is thinned out, rarefied, or even runny. Antonyms for inspissated include words like rarefied, thin, watery, clear, fluid, and liquid. Other words like diluted, liquefied, thinned, and filmy can also be used as antonyms for inspissated. When trying to describe a substance that is not thick or concentrated, one might use these words to help paint a picture of its viscosity, so that others can more easily understand its consistency.