undefined var variable when ajax is called

Question

i am using ajax to return json data. the script goes like this

  var response;
  $.post("GetResults", { Searchterm: Searchterm }, function (data) {

       response = data;

    });

while debugging i see that response is shown as undefined.

I dont want to use the code like below cause i want response to be used in multiple functions:

  $.post("GetResults", { Searchterm: Searchterm }, function (data) {

      var response = data;

    });