Meaning:

“压” means “to suppress,” and “番” is short for “番位,” which originated from the Japanese language and refers to “the rolling of credits” at the end of a movie or TV show. In common practice, top A-listers always appear on top of the credits. This term, often used by fans, refers to the scenario where an actor is ranked lower on the credits than another who is less of a big-shot, or overshadowed in a poster for the project. Sometimes, it also refers to the scenario where the most famous actor is not given the leading role in a movie or show. Such a thing would result in a squabble between fans of different actors, if not a feud between the actors themselves.

Example:

A: 据说最近很火的一部电视剧本来找了佟丽娅演女二号，结果粉丝不满压番，她就没演。

Jùshuō zuìjìn hěn huǒ de yībù diànshìjù běnlái zhǎo le tónglìyà yǎn nǚèrhào，jiéguǒ fěnsī bùmǎn yāfān，tā jiù méi yǎn。

A popular Chinese TV show reportedly had cast Tong Liya in the supporting role, but the actress backed out after her fans got irritated that she was not cast in the leading role.

B: 你说的是《三十而已》吧，现在的演员演得很好，佟丽娅未必比她强。

Nǐ shuō de shì 《sānshí éryǐ 》ba，xiànzài de yǎnyuán yǎn de hěnhǎo，tónglìyà wèibì bǐ tā qiáng。

I guess you’re talking about “Nothing But Thirty.” The actress who plays the role has done a great job, and Tong actually couldn’t have done better.