A half-brother is a term used to refer to a male sibling who is related to you through just one parent. There are several synonyms for this term, such as "stepbrother," which refers to a male sibling that is related to you through the marriage of a parent or stepparent. Another synonym is "brother by another mother," which refers to a male sibling that you share a father with but have a different mother. Other synonyms include "half-sibling," "blood relative," "kin," and "family member." It's important to note that the term "half-brother" should be used with sensitivity, as it can have different meanings and implications for different individuals and family dynamics.