Two methods of preparing fish or meat in Japanese cuisine are called "tataki" or "tosa-mi". In Japanese, "tataki" means "pounded" or "hit into pieces".

In the first "tataki" method, the meat or fish is seared very briefly over a hot flame or in a pan, and can be briefly marinated in vinegar, sliced thin, and seasoned with ginger (which is ground or pounded into a paste, hence the name). Food so prepared can also be served with soy sauce and garnishes like a sashimi.

In the second "tataki" method, it is the food that is "hit into pieces". Fish such as tuna or horse mackerel are chopped and mixed with garnishes such as garlic, ginger, green onions or shiso leaves. Soy sauce may be poured over the chopped mixture before consumption.

More Info: en.wikipedia.org