Teriyaki is the name of a Japanese sauce, as well as food that had been marinated in that sauce and then grilled, broiled, or (occasionally) fried. Apparently the word teriyaki is a combination "teri", meaning lustre or glaze and "yaki" meaning grill or broil. You can buy teriyaki sauce in a bottle, in which case it will be adulterated with the usual food additives, or you can make your own, in which case you'll know exactly what's in it.
Here's what you'll need for basic, traditional teriyaki sauce:
From here it's simple. Just heat all the ingredients in a small pot and simmer for 5 minutes. Cool and use immediately, or strain into a bottle and refrigerate for up to a month. (The straining helps the sauce to last longer, but you'll need a fine mesh strainer.)
By the way, it's the sweetness of the sugar and mirin which are responsible for giving lustre or glaze to the cooked food.
For Japanese cooking, chicken, fish, or shellfish are usually either marinated in, or brushed with, teriyaki sauce before grilling. But you can substitute beef or pork, tofu, shitake mushrooms, or some other vegetable for those traditional meats, or use the tasty sauce as a flavour enhancer in any number of dishes. Let your imagination roam! It's delicious stuff.
I got the translation of teriyaki from
http://japanesefood.about.com/library/weekly/aa080500a.htm
chinakow says: FYI I made this using the sake and sugar and all I can say is "GOOD GOD is this good!!"