A mixture of beaten eggs (yolks, whites, or whole eggs) with either milk or water. Used to coat cookies and other baked goods to give them a shine when baked.

thanks

Also used for double or triple breading stations... as in flour-eggwash-flour or flour-eggwash-panko for breading items such as fried chicken, fish fillets, chicken tenders, scallops, veggies, some tempuras, etc.

I'd have also phrased it as egg and a liquid. Water and milk/cream are, indeed, the most usual. But I've done an egg wash with mustard as the liquid (great for brushing on savory pastries) and other liquids as well.

...as w/ your pork hand-pies!