When describing someone unknown, "whoever" is a commonly used term. However, there are many other synonyms that can be used in place of this term. Some of these include "whomever," "anyone," "anybody," "somebody," "someone," "everyone," "each one," "any individual," and "whatever person." All of these terms represent the idea of referring to an unknown or unspecified person. The use of these synonyms can help to diversify written or spoken language and avoid repetition. It is important to choose the appropriate synonym based on the desired connotation and the context of the sentence.