Sentence:  <WSD>Checkusers</WSD> are allowed to check IP addresses of users, usually to confirm or disprove that one person is editing from several accounts. Although formally one does not have to be an administrator to become a <WSD>checkuser</WSD>, in practice only some administrators receive these rights. 
Meaning of the word marked with <WSD> tags:  A user who is granted access to view the IP addresses of wiki users, so as to identify sock puppets etc.