Byblow is a derogatory term used to refer to an illegitimate child. There are several synonyms associated with this word, including 'bastard', 'lovechild', 'natural child', 'illegitimate offspring', and 'out-of-wedlock child'. These words carry a negative connotation and suggest that the child is unwanted and shameful. However, it is important to note that this term is no longer acceptable and could be considered offensive. When referring to such children, it is best to use more neutral and respectful language such as 'child born out of wedlock' or simply 'child'. It is vital to avoid using offensive and derogatory terms that might hurt people's feelings.