An insult, typically used when angry. The word, despite the word 'nigger', has no racist connotation to it, and can be used when insulting a member of any race.
One that is junior to an accomplished asskisser. They simply cannot get into proximity to kiss the ass so they must be content to hug the butt until the proper opportunity arises.
Batman is a serious asskisser to Commissioner Gordon his sidekick Robin is terribly jealous. Oh well, I guess he just has to pacify himself being a legendary butthugger.