Knock against is a phrasal verb that refers to colliding with something, usually unintentionally. There are several synonyms for the word "knock against," such as bump into, smack into, crash into, collide with, hit, etc. All these terms imply the same action of hitting or striking against something or someone. Another synonym of knock against is jostle. Jostle is used to describe a forceful push or shove between two people or things. It is often used in crowded areas where people are trying to move through a small space. These synonyms provide a variety of options to describe the same action in different ways.