also: はかあな
noun
grave; burial pit
Refers to the physical hole dug for a burial. Often used in the idiom 墓穴を掘る (to dig one's own grave).
墓穴を掘るようなことを言ってしまった。
I said something that was like digging my own grave.
遺体は深い墓穴に葬られた。
The body was buried in a deep grave.
墓 is the general word for a grave or tomb, while 墓穴 specifically refers to the pit or hole itself.
Compound of 墓 (grave) and 穴 (hole). The reading ぼけつ is the on'yomi reading of both characters.