Tataki (also tosa-mi) is a technique of preparing fish or meat in Japanese cuisine. The word can refer to one of two preparations.
In the first, tataki means that a meat or fish is seared or grilled very briefly, then marinated in vinegar, sliced thin, and seasoned with ginger. Food prepared in this style can be served like sashimi.
In the second preparation, tataki means that a fish (often tuna or horse mackerel) is chopped and mixed with ginger, garlic, green onion, or shiso leaves, seasoned with shoyu (soy sauce), and served.