IRC has a concept of "ops" or operator privileges, which are per-channel moderation priveleges. The exact privileges depend on the IRC software running, but it

IRC has a concept of "ops" or operator privileges, which are per-channel moderation priveleges. The exact privileges depend on the IRC software running, but it usually means that you can change the advertised topic message, mute / un-mute users, and kick users out of the channel. Hijack means removing those privileges from someone else and assigning them to yourself.