Get order items full product description

get-order-item-full-product-description

/**
 * You need the order object here.
 * So we'll assume you already have it.
 *
 * To get the order you can call
 * $order = wc_get_order( $order_id );
 */

// Get Order items
$items = $order->get_items();

foreach( $items as $key => $item ) {
	// Get the product
	$item_product = $order->get_product_from_item( $item );

	// Echo the item description
	echo $item_product->post->post_content;
}