customize-product-data-tab.php

/**
 * Customize product data tabs.
 */
function wb_woo_custom_description_tab( $tabs ) {

	$tabs['description']['callback'] = 'wb_woo_custom_description_tab_content'; // Custom description callback.

	return $tabs;
}
/**
 * Customize product data tab content.
 */
function wb_woo_custom_description_tab_content() {
	echo '<h2>Custom Description</h2>';
	echo '<p>Here\'s a custom description</p>';
}
add_filter( 'woocommerce_product_tabs', 'wb_woo_custom_description_tab', 98 );