Bind a function to an object, meaning that whenever the function is called, the value of this will be the object. Optionally, pass arguments to the function to pre-fill them, also known as partial application.
note: If you know you're in an environment where you'll have native Function.prototype.bind (such as node.js) there's really no reason not to just use that. It even does the partial application as described above. Many JS runtimes have it these days. Notable exceptions are Phantom.js and IE8 or older.