What is "underdetermination"

n. The state or quality of being underdetermined

In the philosophy of science, underdetermination refers to situations where the evidence available is insufficient to identify which belief we should hold about that evidence. For example, if all that was known was that exactly $10 was spent on apples and oranges, and that apples cost $1 and oranges $2, then we would know enough to eliminate some possibilities (e.g., 6 oranges could not have been purchased), but we would not have enough evidence to know which specific combination of apples and oranges was purchased. In this example, we would say that belief in what combination was purchased is underdetermined by the available evidence.