var utility = function(){
...
};

//window.jQuery = function(selector, context){
w.jQuery = function(selector, context){
    utility();
};

//(function(window, undefined){
(function(w, undefined){
    var utility = function(){
    };

    //window.jQuery = function(selector, context){
    w.jQuery = function(selector, context){
        utility();
    };

})(window);