If some more information was given in this question, it would have better to answer more accurately. But some of the possible abbreviations for EJ are as follows:
EJ: Electronic Journalism
EJ: Euro Japan
EJ: Edward Jones (investing company is USA, Canada and UK)
EJ: Exajoule
EJ: Electronic Jamming
EJ: Escort Jammer
EJ: Electronic Jockey
EJ: Emergency Jettison
EJ: External Juggler vein
EJ: Economic Journal