Mal de debarquement
Mal de debarquement Syndrome (MDD or MdDS) is a rare condition whose symptoms include continuing imbalance sensation. Travellers often experience this sensation temporarily after disembarking a sea cruise or a long airplane flight, but in the case of MdDS sufferers it can persist for 6-12 months or even many years.
The name of the condition is French for "disembarkation sickness".