Horn in informal verb phrase
If one horns in someone or something, he or she intrudes on someone, or interferes in something in an annoying and unwanted way
She has no right to horn in their marriage.
Employers should not horn in the private lives of their employees.
To interfere somebosy's plan or bussiness
Not working properly
To disrupt someone's plan.
To interrupt something (usually a conversation or discussion).
To take someone's attention away from, or interfere with what they are doing, so that they are unable to do it well
The verb “horn" should be conjugated according to its tense.
The phrase is American cowboy slang from the late 19th century (c.1880) and uses the metaphor of a bull or steer butting in with its horns.