ale·a·to·ry /'ā-lē-ə-ˌtōr-ē/ adj [Latin aleatorius of a gambler, from aleator gambler, dice player, from alea, a dice game]: depending on an uncertain event or contingency as to both profit and loss
the aleatory nature of a lawyer's contingency fee arrangement
Merriam-Webster’s Dictionary of Law. Merriam-Webster. 1996.