Below is my snippet saved in /Library/Application Support/Sublime Text 3/Packages/User
<snippet>
<content><![CDATA[
define([
'jquery',
'underscore',
'backbone',
], function($, _, Backbone) {
"use strict";
});
]]></content>
<tabTrigger>define</tabTrigger>
<description>define</description>
</snippet>
In a JS file writing define then tab does nothing.