A person who likes to go "all in" when playing 'No Limit' poker far more than is probabilistically reasonable - i.e., than is justified by the odds. An alliniot might e.g. typically join an online poker table and go "all in" on every hand when playing No Limit Texas Holdem, until he eventually loses & leaves.
Derivative of "all in" (as in going all in) plus idiot.
That "Alliniot" can't resist going all in yet again, with his Jack 4 off (suit) pre flop. What a donkey!!!