A stacked wild is essentially a wild symbol that can cover an entire reel when it drops. They are normally in bands of 2, 3, 4, or 5 symbols. Some slot games have the possibility of getting stacked wilds on every reel, while others have them appearing on specific reels. Many slots that have the possibility of getting stacked wilds on every reel have high variance.
Other slots have stacked wilds exclusively appearing in the Free Spins bonus feature, and when you combine these with multipliers the potential for a big win is significantly increased. In some cases big wins with stacked wilds can pay out a life changing amount of money.
Spartacus Gladiator of Rome
WMS
Lucky Larry's Lobstermania 2
IGT
Siberian Storm
IGT
Zeus
WMS
Wolf Run
IGT
Shining Crown
EGT
Shadow of the Panther
High 5 Games
Giant's Gold
WMS
White Falls
High 5 Games
Zeus 3
WMS
Dangerous Beauty
High 5 Games
Super Hot Fruits
Inspired Gaming
Fu Dao Le
Bally
Kronos
WMS
Sirens
High 5 Games
Dragon Spin
Bally
Crystal Forest
WMS
China River
Bally
Zeus 1000
WMS
Super Red Phoenix
Bally
Stacked wilds work in more or less the same way as expanding wilds. However, stacked wilds will have a single wild symbol falling on a reel before it expands to fill in the indicated spaces around it. Stacked wild might expand to fill in the entire reel or they might just expand to fill the top or bottom section of the reel. Each game has different rules attached to such symbols, and these rules can be found in the paytable of every game. To access the paytable of any given game, look for a button within the gaming interface that indicates info, menu, paytable, or similar.
Stacked wilds are one of the newer slot features - this image shows a stacked wild on the 2nd reel in the Thor slot by Playtech
Essentially, stacked wilds are still wild symbols, and they therefore help to complete winning combinations by substituting other symbols on the reels. However, stacked wilds have a much greater potential of forming winning combinations because they cover a larger area than normal wilds which normally only cover a single part of a reel.
Stacked wilds are one of my favorite slot features as the games are generally more volatile and offer the chance for bigger wins. If you see that a slot offers stacked wilds, it is generally a game that result in some big payouts when you get lucky. Try them out on a free play game to get the hang of them. The Kiss slot machine by WMS and Western Belles by IGT are two games that feature stacked wilds. Why not try them out?