Spirants are sounds that are produced by forcing air through a narrow passage in the mouth or nose. These sounds are usually fricatives or affricates. There are several synonyms for spirants, including fricatives, sibilants, and hissing sounds. Fricatives are consonant sounds that are produced by forcing air through a narrow space created by two articulators in the mouth. Sibilants are a type of fricatives that produce a hissing or rushing sound. Some examples of sibilants include the "s" and "sh" sounds. Hissing sounds, on the other hand, are a general term for sounds that resemble the noise a snake makes when it hisses. Overall, these synonyms help to describe the various sounds that are produced by spirants.