Add this code to your child theme’s functions.php file or via a plugin that allows custom functions to be added, such as the Dessky Snippets plugin. Please don’t add custom code directly to your parent theme’s functions.php file as this will be overwritten completely when you update the theme.

The following snippet will replace the description tab with a custom function.

/**
 * Customize product data tabs
 */
add_filter( 'woocommerce_product_tabs', 'woo_custom_description_tab', 98 );
function woo_custom_description_tab( $tabs ) {

	$tabs['description']['callback'] = 'woo_custom_description_tab_content';	// Custom description callback

	return $tabs;
}

function woo_custom_description_tab_content() {
	echo '<h2>Custom Description</h2>';
	echo '<p>Here\'s a custom description</p>';
}