(informal) a scenario in which all options/outcomes appear equally appealing or likely to occur, thus offering no basis to make a decision or providing a fair chance;
e.g. It is a toss-up between these two destinations for our vacation.
(noun)
the action of tossing/flipping a coin in order to choose between two options;
e.g. They resorted to a toss-up to decide which route to take.