English No. In the classical sense, it is not. Arbitrage betting is a situation in which a player is guaranteed, with 100% probability, to come out of an arbitrage bet at least without a loss and, in most cases, with a good win.
Polish middles, on the other hand, allow for one, albeit doubtful, outcome to arise, which may reduce the player's bankroll. This is described in detail in the article about Polish middles.
So why do we discuss them on the website? It is very simple – Polish middles use the same principles as ordinary middles, where several oppositely directed events intersect, giving the player the opportunity to earn 5-10 times more (on average; there can be imbalances) than to lose.
The method, although not absolute from the standpoint of reliability, is potentially very profitable. And if you know how to find Polish middles (and we do), you can earn quite well from them.