1 : not paid at an expected or required time
She reminded him that the rent was overdue.
He has many overdue bills.
2 : not appearing or presented by a stated, expected, or required time
The train is 10 minutes overdue.
Her baby is overdue by one week. [=her baby has not been born yet and it is a week since its birth was expected]
an overdue library book
3 — used to say that something should have happened or been done before now
His promotion is long overdue. = He is long overdue for a promotion. [=he should have been given a promotion by now]
Repairs on that building are long overdue.