When describing something that is not similar to another, there are many different words that can be used. Some alternatives to "not similar" include "dissimilar," "different," "unlike," "distinct," "divergent," "opposite," "contrasting," and "various." These words can help to convey a more nuanced and precise meaning, depending on the context and the nature of the difference between the two things being compared. By using synonyms for "not similar," you can make your writing more interesting, engaging, and effective, as well as avoid repetition and enhance clarity.