The term 'Arrogant Newcomer' can be summed up as an UPSTART, or someone who is new to a situation and behaves in a conceited manner. This person is likely to be inexperienced and overconfident, believing they know more than they actually do. They may also be overly ambitious and pushy, expecting to be given preferential treatment due to their newness. This type of behavior can be seen as disrespectful and disruptive, and can lead to tension and conflict in the workplace.