Closing line
The closing line is the final price and line a market offers before an event begins.
In plain English
By kickoff a market has absorbed lineups, weather, injuries and the weight of money. That makes the closing number the most informed public estimate available, and a common benchmark for judging an earlier price.
Example
A side is +3 in the morning and closes at +1.5. The closing line is +1.5.
Why it matters
It is the fairest available yardstick for whether a bet was placed at a good price, because it is set after the market has learned nearly everything it will learn.