currently the meta is swarming the field with 3 monsters and protecting your monsters with srh and enemy controllers ex ( hammershark beatdown , naturia , red eyes from the grave using Red eyes spirt and red eyes insight , in the future the meta might be machines, or decks based on using treefrogs for tributes .
META technically is Most Effective Tactic Available. In Duel Links meta refers to top deck styles with highest win rate in pvp dueling.
The meta keeps changing as Konami puts more cards into the game from the real life Yugioh card pool, with new cards in suddenly making a deck much stronger and now the new meta. Calling something meta is an opinion, but some decks are clearly super powerful.