I looked up Teriyaki in several online sources to get a definition as Lugaru's explanation was one I'd never heard. He is correct however, and I learned something new.
The result of my search is that teriyaki means teri - glazed or shiny, yaki - broiled.
Traditionaly, it seems that a teriyaki marinade is a combination of soy sauce and mirin. I don't use alcohol in my home and substitue crushed pineapple and brown sugar for the sweet mirin wine. The definitions also stated that the soy sauce was highly seasoned, usually with garlic, ginger, and onion. But those ingredients are optional.
For my teryaki, I start with a little water and add lite soy sauce (Kikoman brand is what I prefer), Splenda, a bit of mollases, granulated garlic powder (it takes too long for fresh garlic to give up its flavor in the application, IMHO) chopped fresh onion, powdered ginger, crushed pineapple with lite syrup, and black pepper. I first add the pineapple and soy sauce to the water and taste until I get the flavor I want. I then add a little of the other ingredients, stirring and tasting as I go so as to keep a flavor ballance somewhere between sweet and savory. When the flavor is right, I add the meat and let marinate.
Meats that can be used with teriyaki include seafood such as shrimp, scallops, firm-fleshed fish, beef, pork, chicken, turkey, etc. After the food has marinated for a couple hours, the food is either grilled or broiled.
If I'm grilling, I'll often add hardwood to the charcoal and cover the grill, turning the whole thing into more of a barbecue. But this is trick if you are cooking small items such as shrimp. You don't want to overcook them.
The marinating liquid can be brushed onto the food as its cooking to enhance the flavor and further glaze it.
Hope this helps.
Seeeeeya; Goodweed of the North
