noun
1.
( BrE ) a vehicle that has been so badly damaged in an accident that it is not worth spending money to repair it
2.
[ sing. ] ( informal ) a period of time during which you do not achieve anything :
With meetings and phone calls, yesterday was a complete write-off.
3.
write-off (of sth) ( business ) an act of cancelling a debt and accepting that it will never be paid