Does this keyword have some kind of special ability(like scout)? Thx in advance.

Right now, no, but that doesn't mean there will never be a game effect from them.

Those words on the cards like Skaven, Knight, Cavalry etc. are called traits and sometimes other card effects look for other cards with that trait. For example, Greyseer Thanquol looks for any other Skaven units in play and gets an attack bonus from them.

Scout is a bit different in that it has a predefined meaning in the main rules.

Now I am wishing Knights had their own Totem of Gork....