I have heard League of Assassins members call R'as al Ghul something like Malich before, and I thought it was unique to the now deceased R'as al Ghul, but I heard them call Malcolm Merlyn Malich as well. I also heard it on Justice League: Flashpoint Paradox, mentioned by Aquaman's men (unless I am dead wrong). So, does it mean master, your highness or something like that? Also, how is it really pronounced?
I've just re-watched a few episodes of Arrow plus all of Flashpoint Paradox, and I'm pretty sure what you are hearing these people says is "my liege".
This is just a normal, though slightly archaic, English word for addressing the person to whom you owe allegiance: a king, emperor, feudal lord, etc. It's pronounced with a "soft g" sound, that is, it sounds like "my leej" or possible "my leezh", depending on the accent.
noun 1. a feudal superior or sovereign.
Both the League members and Aquaman's men alternate between calling their boss "my Lord" and "my Liege", which are roughly equivalent, though one is slightly more formal.
I don't know if you've personally heard the word before, but if it's pronounced like "Malik", or "Malek", then this word means "king" in Arabic (You were pretty close with "master").
I doubt that it sounds like "my liege" since the character's history is tied to Arabic in many ways, so I think this makes more sense. R'as al Ghul literally means "Head of the Demon" in Arabic and he was born somewhere in Arabia in his origin story.