Learn English – More compelling way to describe something as “The Next Big Thing”

Expending disproportionate effort on trivial matters is sometimes known as bike­shedding, or Parkinson’s Law of Triviality.

Jeff blogged about the phenomenon in the context of it being a problem on Stack Overflow...

In some contexts, the word you're looking for is "understatement".

When done intentionally, it could be "irony".

Try this: "Big? That's an understatment!"

Irony: "I have a flight booked from NY to London. I get nervous flying over the big pond." (Atlantic Ocean)