Meaning: Wasted or lost completely, often referring to money, time, effort, or resources.

Usage in Example Sentences:

1. “All the money he invested in the project went down the drain when the company closed.”
2. “If we don’t meet the deadline, months of hard work will be down the drain.”
3. “Leaving the water running while brushing your teeth is like letting money go down the drain.”

Origin:
The idiom originates from the literal image of something disappearing down a drain, such as water, which is irretrievable. It began being used metaphorically in the 20th century to describe irrecoverable losses or wasted efforts.