Steamer
A steamer is a selection whose odds are shortening quickly — the price is "steaming in". A team that opened at 2.10 in the morning and is 1.75 by lunchtime has steamed, and the cause is always the same mechanically: bookmakers are taking more money on that outcome than their opening price anticipated, and they cut the price to rebalance their liability.
What a steamer means is less settled than what it is. Sometimes the money is informed — team news that has not broken publicly, sharp bettors acting on a genuine mispricing. Sometimes it is simply weight of popular opinion: a heavily tipped selection steams because thousands of small stakes arrive on it, with no new information anywhere in the chain. The market cannot tell you which kind of move you are watching; it only records that the move happened.
Two practical points follow. First, a steamer is not evidence a bet wins — favourites that steam still lose at roughly the rate their final price implies. Second, if you liked a price and it steams before you take it, the value you identified has partly or wholly gone; chasing a move after it has happened is paying yesterday's price plus a premium.
We track the day's biggest moves, alongside our model's own probability for each one, on the steamers and drifters page.