Formal:
* Interject: This implies a sudden, often forceful, interruption.
* Interpose: This suggests a deliberate interruption to make a point or express an opinion.
* Interrupt: This is the most general and neutral term for interrupting.
* Cut in: This is a more informal way of saying "interrupt."
Informal:
* Butt in: This is a slang term for interrupting rudely.
* Jump in: This implies a sudden, enthusiastic interruption.
* Chime in: This suggests a friendly and casual interruption.
* Break in: This implies interrupting to make a point, often forcefully.
Other options:
* Cut off: This implies stopping someone mid-sentence.
* Sidetrack: This implies changing the subject of the conversation.
* Overtalk: This implies talking over someone else.
The best word to use will depend on the specific situation and the tone you want to convey.