The term "toplevel" is often used to describe something that is at the highest level or rank. However, there are numerous synonyms that can be used in its place to add diversity to your language. Some of these synonyms include "highest", "uppermost", "supreme", "leading", "upper", "primary", "chief", "main", and "topmost". Each of these terms can be used interchangeably with "toplevel" to convey the same message or meaning. Using synonyms not only adds variety to your writing but also helps to avoid redundancy and repetition.