1. 长篇大论;滔滔不绝的讲话
If you refer to a long speech by one person during a conversation as a monologue, you mean it prevents other people from talking or expressing their opinions.

2. 长篇独白;独角戏
A monologue is a long speech which is spoken by one person as an entertainment, or as part of an entertainment such as a play.

1. a (usually long) dramatic speech by a single actor

2. a long utterance by one person (especially one that prevents others from participating in the conversation)

3. speech you make to yourself

Synonym: soliloquy