This disabled button is enabled after three seconds via JavaScript (not jQuery).

delayed-button.html

<button id="form-submit" type="submit" class="button button-primary" disabled>Send</button>

<script>
  setTimeout(function() {
    var btnSubmit = document.getElementById('form-submit');
     if (typeof btnSubmit !== "undefined") {
       btnSubmit.disabled = false;
     }
}, 3000);
</script>

A simple way to help prevent automated form submissions (in conjunction with other methods).