Days a game got far more negative Steam reviews than usual, mostly negative ones: what players call a review bomb.

• A flag says the reviews were unusual, not why. Some waves are about a real problem with an update; the news posted that day is shown beside it.
• Steam later hides some off-topic reviews from its score; this counts the reviews its graph showed when we read it.
• Games read monthly can be flagged up to a month late.

Source: Steam store, store.steampowered.com/appreviewhistogram. Full methodology