1. Any open threshold of an enclosed passageway, into which things or
people may fall due to gravity (e.g. a garbage chute), be pulled by suction (e.g. a vacuum tube), or travel without any assisting force (e.g. a covered bridge).
2. A
depressed section of the ground or floor formed in a controlled manner (e.g. excavation for i.e. building an in-ground pool) or in an unstable manner due to erosion (e.g. sinkholes) or material damage (i.e. a bathtub falling to the floor beneath).
3. An opening in vulnerable material caused by penetration (i.e. a
nail in a tire) or surface wear (i.e. rusted iron).
4. A cavity that is otherwise filled by a mating object (e.g. a screw hole).
5. A psychological emptiness typically associated with grief (e.g. a hole in my
heart).
6. (vulgar) Another name for e.g. the mouth or the
anus.