Pit
chasm
chasm
The word deepen means to cause to become more deep. For example, if you have a hole that is five feet deep and you dig it out so that it becomes six feet deep, you have deepened the hole.
Well, cavern...
A four letter word for not shallow is deep.
The Greek word that chasm came from is the word abyss. An abyss is a very deep, deep hole that is so deep it never seems to have a bottom.
hole
ace
shallowShallow
coma
pore
a hole door