Wild symbols have been attached to the reels of slot games for decades now, however every now and then a slot game designer will devise a brand new type of wild symbols which will perform some additional task whenever one or more of them have been spun in.
One slot game designers who slots games often come with a unique type of wild symbols is NetEnt, and when playing at a casino site offering all of their slot games be on the lookout for their EggOMatic slot which offers something know as a Spreading Wild symbol.
When you do play a slot with a spreading wild reel symbol whenever that symbols spins in it can spread across the screen either horizontally or vertically and as it spreads across the screen it will then turn every adjacent standard reel symbols it touches into wild symbols.
The more reel symbols that are turned into wild symbols via the spreading wild symbol the more chance you will then have of forming one or more than one winning combinations, if a slot has several of those symbols in play you will find those slots can offer some very high valued winning payout when you get lots of those reel symbols spinning in.
You will often find however that those types of slots offering that special wild symbols often come with a fixed pay line playing structure, so whilst you will always have the maximum number of payline in live play when playing those slots you will need to have enough cash in your casino account to be able to put into play all of those slots pay lines!