Huge
Enormous
な adjective
Something that is endlessly big isn't just big, but huge and enormous.
This word is often used in contexts that involve money, but it can also be used for other things like time, energy, and data.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
道路建設には莫大な費用がかかる。
Road construction costs huge amounts of money.
このままでは、コストが莫大になる可能性があります。
If this situation continues, the cost could be enormous.
カニの像は美しいが、莫大な資金が使われたことについてはだれも喜ばないだろう。
The crab statue is beautiful, but no one will be happy with the huge amount of funds spent on it.