The word icing has two main meanings:

1. A sweet, creamy coating spread on cakes, cookies, and pastries. Icing is made by mixing powdered sugar with butter, milk, or cream cheese to create a smooth spread that hardens slightly as it dries. A birthday cake gets its colorful top layer from icing, which bakers can flavor with vanilla, chocolate, lemon, or almost anything else. Some people call it frosting, though icing tends to be thinner and sets harder than fluffy frosting.
2. In ice hockey, an icing violation occurs when a player shoots the puck all the way down the ice and across the opponent's goal line without anyone touching it. The referee stops play, and the offending team faces a faceoff in their own defensive zone. This rule prevents teams from just whacking the puck down the ice whenever they feel pressured. It keeps the game moving and strategic rather than turning into a contest of who can hit the puck the farthest.

The phrase icing on the cake means an extra good thing added to something already good, like winning a trophy and then finding out you also get a pizza party.