The term "signed on" has many possible synonyms that can be used to convey a similar or related meaning. Depending on the context, some alternatives to "signed on" include "joined," "registered," "enlisted," "enrolled," "committed," "accepted," "agreed to participate," or "became a member." In some cases, other phrasing such as "signed up," "signed a contract," or "signed an agreement" may be more appropriate. By using varied synonyms for "signed on," writers and speakers can avoid repetition and add nuance to their language, while still conveying the core concept of making a commitment or agreement.