Literally it's "reply" together with a term for an actor performing a work that they also wrote. And together the phrase is net slang for sock-puppeting.
> 自作自演 (jisakujien ; self-made self-staged ; for example, used for the act of creating a staged situation and then acting as if it were genuine)
The original meaning was a screenwriter-actor performing the script they wrote, which is a perfectly fine thing to do. It can mean 'sockpuppeting', too, and that other use might be more common nowadays, though.
一石二鳥 (issekinichou ; literally: one stone, two birds ; I'll let you guess the meaning (yes, it's very close to an expression in English))
自業自得 (jigoujitoku ; reap what you sow)
自作自演 (jisakujien ; self-made self-staged ; for example, used for the act of creating a staged situation and then acting as if it were genuine)
自問自答 (jimonjitou ; answering one's own question)
自暴自棄 (jiboujiki ; self-abandonment)
自画自賛 (jigajisan ; singing one's own praises)
自給自足 (jikyuujisoku ; self-sufficiency)
自由自在 (jiyuujizai ; free/unrestricted)
(Yeah, I have a thing for the 自◯自◯ ones)