/**
 * Snippet Name:	WooCommerce Change In Stock Text
 * Snippet Author:	ecommercehints.com
 */

add_filter( 'woocommerce_get_availability', 'ecommercehints_change_in_stock_text', 10, 2);
function ecommercehints_change_in_stock_text( مانده , $availability  ) {

    if ( $product->is_in_stock() ) {
        $availability['availability'] = __('Plenty available!', 'woocommerce'); // Customised text
    }
    return $availability;
}