Remission refers to the absence of active disease. There are two types of cancer remission. Complete remission (or undetectable disease) refers to a cancer that has no signs or symptoms, and no evidence of cancer can be found on a physicial exam by a doctor or through radiological tests. Partial remission refers to a cancer that is still detectable, but has decreased in size.
With complete remission, some doctors use the terminology "NED" - which stands for "no evidence of disease."
Remission does not mean that a cancer has been cured. There may still be cancer cells present that are undetectable by tests we have at this time.
If a cancer returns after it has been in remission, it is defined as a recurrence of that cancer.