There is another use of “mug”. If someone has been a mug he has behaved badly or made a big mistake, and the word can also refer to something foolish (estupido). Examine these:
• Smoking is a mug´s game (fumar es cosa de bobos).
• I have been a mug (he sido bobo): I trusted Mr. Sanchez.
Another use as a verb: to mug someone is to attack and rob (atracar). An example:
• He was mugged (fue asaltado en) in New York.
So there are many things in life that are a mug´s game. One has to be careful not to be mugged, and also to avoid being a mug.