dramatic monologue

US /drəˌmæt.ɪk ˈmɑː.nə.lɑːɡ/
UK /drəˌmæt.ɪk ˈmɑː.nə.lɑːɡ/
"dramatic monologue" picture
1.

a poem in the form of a speech or narrative by an imagined person, in which the speaker inadvertently reveals aspects of their character while describing a series of events.

:
Robert Browning is famous for his use of the dramatic monologue in poems like 'My Last Duchess'.
The actor delivered a powerful dramatic monologue that captivated the audience.