Uncovered in cooking means cooking with no lid or covering.
If the meat loaf is having trouble cooking all the way through, and the dish needs an extended amount of cooking time. It is recommended to cover the meat loaf with foil or something similar to keep the dish from becoming dry.
Covered, you need a steam to form for the rice to cook.
broiler- set your oven to broil
It will dry out over time as long as it is uncovered, if it is covered it will get moldy
Cover to cook and keep all moist; uncover if you want some 'crust' on top.
Cooking it covered will cook it faster as it keeps the heat in the food, and if your cooking meats will help to keep the juices in. Uncovered foods will bake faster on the outside possibly buring before the inside gets fully cooked.
soup and sauses are generally enjoy for fluidity, cooking uncovered allows fluid to evaporate. you would not enjoy a hot bowl of chicken noodle paste would you?
you're a medium
It really makes no difference. It can pop out while it cooks if it is on too high. Put a lid on it if you are worried about that.
Possibly means 'uncovered.' See link below:
Gs means grams in cooking.
OVB is not a cooking term, but is a brand of silverware.