In the Weebly Editor click on Pages, and then select the page name from the left side column. Click on SEO Settings and then scroll down to find the HEADER CODE window and copy the following rules into that window, then Publish your site. The Menu will still be visible in the Editor but not in the published public site.

<style>
@media screen and (max-width: 992px) {
    .hamburger {
        display: none !important;
    }
}
</style>