<?php
add_filter( 'woocommerce_product_tabs', 'woo_rename_tabs', 98 );
function woo_rename_tabs( $tabs ) {
//$tabs['description']['title'] = __( 'More Information' ); // Rename the description tab
//$tabs['reviews']['title'] = __( 'Ratings' ); // Rename the reviews tab
$tabs['additional_information']['title'] = __( 'Specifications' ); // Rename the additional information tab
return $tabs;
}