(noun)
something that resembles a hood in appearance, such as a marking or structure on an animal's head or neck or a garment similar to a scarf that is worn over academic gowns to indicate the degree and/or institution of the wearer,
e.g. The cobra raised its hood to show that it was agitated. He wore a deep purple hood with his robes.
(noun)
something that resembles a hood in its protective function, such as a cover for machinery or parts of a vehicle, or an overhead canopy that sucks away harmful fumes, smokes, or dust;
e.g. She opened the hood of the car to check the engine. Always work with these chemicals under the hood so that you don't inhale too much of them.
(noun)
(informal) a neighborhood in a city, especially the neighborhood that one comes from or one in the poorer, older part of a city;
e.g. They have lived in the hood for many years.