Queer is a term most often used outside the gambling world but it has also become a part of the casino terminology.
As an everyday word, queer stands for something odd or unconventional. For that reason, when it comes to casino slang, the term queer stands for money that feels odd. In other words, it refers to counterfeit money.
However, outside gambling establishments, the word queer is used as a derogatory slur to refer to someone who is not heterosexual, which is important to remember so that someone doesn’t misinterpret your intent and takes offence at the word.