When something contradicts an established precedent or prevailing custom or practice, it is said to “break with precedent” or “go against precedent.” Another common collocation is “without precedent” in reference to something not supported by a prior example or ruling.

What is the meaning of to set a precedent?

: to decide something that will be used as an example or rule to be followed in the future The ruling in the case is likely to set a precedent for how future cases are decided.

How do you set the precedent?

Establish a usage, tradition, or standard to be followed in the future. For example, He set a precedent by having the chaplain lead the academic procession. The word precedent here signifies a previous instance or legal decision upon which future instances are based, a usage dating from the early 1400s.