Pinterest Share – Share with Image Alt tags rather than post description

Yes its possible you have to customize the javascript code.

edit the plugin js file

wp-content/plugins/wwm-social-share-on-image-hover/js/wwm_custom.js

It may be minified you have to beautify it.

following code

if (jQuery(e).hasClass("wwm_pinit")) {
        var l = "https://pinterest.com/pin/create/bookmarklet/?media=" + encodeURIComponent(u) + "&url=" + encodeURIComponent(a) + "& is_video=false&description=" + o;
        wwm_common_share(l)
    }

change to

if (jQuery(e).hasClass("wwm_pinit")) {
        var l = "https://pinterest.com/pin/create/bookmarklet/?media=" + encodeURIComponent(u) + "&url=" + encodeURIComponent(a) + "& is_video=false&description=" + jQuery(e).parent().prev("img").attr("alt");
        wwm_common_share(l)
    }