Being hostile to something or someone can be expressed in several ways using synonyms. One of the most common synonyms is being aggressive towards or showing aggression towards. Another would be being antagonistic or exhibiting antagonism towards someone or something. Someone could also be described as being unfriendly or confrontational towards someone else. Being inhospitable is another way to describe a hostile attitude towards someone, as well as being unwelcoming or uninviting towards them. Lastly, being combative or displaying combative behavior towards someone or something also falls within the scope of being hostile towards them.