Expanding Wild
A wild symbol that stretches to cover an entire reel (or row) after it lands, turning every position it fills into a wild.
Definition
When an expanding wild appears, it grows from a single symbol to cover the full reel or a whole row, so each of those positions acts as a wild for that spin. This can complete many paylines or ways at once and is a common way for slots to deliver a large single-spin win. Expanding wilds are frequently paired with free spins, where an expanded wild may also become sticky. Despite the visual payoff, the frequency of the expanding trigger is set within the overall math so the house retains its margin over time.
Worked example
A single wild lands on reel three, then animates to fill all three visible rows of that reel. Every payline passing through reel three now treats it as a wild, so multiple lines can pay from the one expanded symbol.
Why it matters
For a learner, this clarifies how one symbol can transform a modest spin into a big one. For a professional, expanding-wild frequency and reel placement are levers that concentrate volatility into rarer, larger wins.