Meaning:
“大” means “big,” and “女主” refers to “the heroine of a movie, TV series or book.” Chinese netizens use this term to refer to a strong female lead in movies and TV shows. It’s not just that the character has a lot of screen appearances, but that such a protagonist exudes confidence and courage in pursuing her goals and accomplishes things on her own. She is not “your average girl” serving only the function as the male lead’s “love interest.”
Example:
A: 你喜欢追什么类型的剧？
Nǐ xǐhuan zhuī shénme lèixíng de jù？
What kind of TV shows do you like?
B: 我喜欢有大女主的剧。
Wǒ xǐhuan yǒu dànǚzhǔ de jù。
I like TV series with strong female leads.