NOTE: Not all events offer the cashout option.
To "Cashout" means cancelling your bet before the event finishes, for a fraction of the projected outcome.
In order to cashout your bet, first you need to go "My Bets" tab that you can find on the right side of the page, as indicated below.
Upon pressing that button, you'll see all your active bets, and the amount you'll receive if you cash out.
As seen above, this can help you limit your losses or take a fraction of your win. In some events, you can cash out partially, in the button seen on the right of cashout.