to decrease quickly or be very unsuccessful:
Not long after the chairman resigned, shares in the company tanked.
2 [intransitive] British English informal
to travel very fast in a car or vehicle
3 [intransitive] informal
to fail badly and be very unsuccessful:
His last film tanked in the States, but did well in the UK.
4 also tank it [transitive]
to deliberately lose a sports game that you could have won
tank upphrasal verb
especially American EnglishTTC
to put petrol in your car so that the tank is full