multi-accounting
used to describe the practice of entering multiple accounts (screen names) into the same online poker tournament. 

 The sole purpose of multi-accounting is to create an advantage by offering one player multiple chances to advance to the later stages of a tournament where the significant money is.

  The term was first widely used after high profile online players JJprodigy and ZeeJustin were banned by multiple online poker sites for the practice.

 It should be noted that playing on an account other than your own is not in itself multi-accounting so long as it's the only account being used in the tournament or cash game.
ZeeJustin was banned from pokerstars and partypoker for multi-accounting the big MTTs.