Text inside of the hidden label.

Yes, you can write "DO NOT FILL" instead of "Address" like below:

<tr style="display: none;">
    <th>
        <label for="address">DO NOT FILL</label>
    </th>
    <td>
        <input type="text" name="address" id="address">
    </td>
</tr>

But, I think it's better to take user's input for two basic reasons:

1. A form that says "DO NOT FILL" or "LEAVE ME BLANK" doesn't sound legit, especially to visually impaired users who are trusting screen readers for browsing. They may find it suspicious or confusing unless you explain the whole spam story.

2. If your form asks a simple question like "2+2" or "what's the current year", you are only improving your chances of fighting spam.

You can still keep this input field hidden as you don't want most visitors to see it anyway. This way you can address both users, those who see your page, and those who don't.

<?php
if ($_POST["answer"] != "" && $_POST["answer"] != date('Y')) {
    echo "Your form submission has an error.";
    exit;
}
?>

<tr style="display: none; visibility: hidden;">
    <th>
        <label for="answer">What is current year?</label>
    </th>
    <td>
        <input type="text" name="answer" id="answer">
    </td>
</tr>

Make sure you add the CSS property visibility: hidden along with display: none as some screen readers like Window-Eyes ignore the later.

Hope this helps!