A person so useless on this planet that the mere fact of them breathing is a waste of oxygen.
"O2 Thief"; someone who wastes or doesn't deserve the air that they steal. Often incompetent; may be overweight but always useless. Usually talks a load of shite. (Forums) time-wasting, argumentative bandwidth-burglar or incorrigible wibble-merchant. ARRSE DS solution: do not respond.
So reads the usual references of the term. Unfortunately most of the planet could fall under that description. Admittedly some people like RMPs and RAF Police are born into that category but who is to judge that anybody be reduced to the status of Oxygen Thief? I suggest that a few ground rules be established.
Pavarotti was overweight but he could croon a good melody. He was also worth a packet. If everyone who talked shite was reduced to Oxygen Thief then all of the Houses of Parliament would be similarly condemned. All Subalterns, Midshipmen and Pilot Officers would also be tarred with the same brush along with Local Government Officers, Health and Safety officials and Time Share salesmen. Hell! Let's just kill 'em all!