Any improvised object used to forcibly gain entry into a locked/secured structure or vehicle when the person does not immediately available to them appropriate tools when entry is needed. Such tools may be a hammer, brick, coat hanger, steel toed boots, your body, or any other object which will allow you to gain entry.
More often then not, using a "Mexican lock pick" will damage the entry or property that the person is trying to gain access to. As such, it should be a last resort used to gain entry.
Person 1: "I locked my keys in my car yesterday, so I had to use a mexican lock pick."
Person 2: "What's that?"
Person 1: "A hammer."