noun - An operator on an IRC network. They are usually in charge of making sure that the network runs smoothly.
Sometimes given an bad name for either abuse of their power, or negelecting their responsibilities.
verb - to obtain oper privileges on an IRC network.
oper up, and relink the services
somebody get an oper in here and ban that spammer
Derived from OP meaning Original Post. OPer, when used on internet forums, means Original Poster - meaning the person who started the thread.
Dude, did you even read what the OPer wrote before you made that comment?