Maisir (Maysir) refer to an arabic term ( ميسر ) which is a game of chance (Gambling) was played by arab before islam.
The Maisir (Maysir) arises when one party profits at the expense (loss) of the other, in an uncertain event. Earnings through it have been strictly forbidden by Sharia (the islamic law).
Gambling and all games of chance have been strictly prohibited by the Quran.
“They question thee about strong drink, and games of chance. Say: In both is great sin, and (some) utility for men; but the sin of them is greater than their usefulness.” (Al-Quran 2:219)