The word nasty refers to food that is decaying or does not look, smell or taste good for some reason. In this case, it may be a matter of personal taste.
Ex: Those vegetables you cooked are so nasty! They are overcooked, mushy, and they are leaving a bitter taste in my mouth.
Ex: How long has that meat been sitting on the counter? It smells nasty, and if it gets rotten dangerous bacteria can grow on it.
The word nasty can also refer to a person, person, or thing that is difficult, dangerous, or unpleasant to be around. In this case, it is a synonym for rotten.
Ex: Our neighbour's dog is gorgeous, but he is nasty. He has already bitten three children in the neighbourhood and growls at anyone who comes near him.
Ex: Jane is spreading nasty rumours about other students. As a rule of thumb, she should not be so mean to the people she sees at school every day.
The word omnivorous refers to eating both plant and animal foods. The word can refer to a person or animal who is said to be an omnivore.
Ex: Some dinosaurs are said to have been omnivorous. However, the most dangerous ones were carnivorous. This means that they only ate meat.
Ex: Vegetarians are not omnivorous. They feel that meat is detrimental to their health and the well being of the natural world.
The word omnivorous can also refer to having a curious mind. In this case, it refers to a person who takes in any and all information.
Ex: Kelly's appetite for books is omnivorous. She would rather read a good novel or biography than do just about anything else.
Ex: Victoria is an omnivorous observer. She does not say much, but she watches everything closely and writes about it later.