Definition

Overlooked, underestimated, or not given proper attention or recognition by the general public; ignored by people who should know better.

Example Usage

That startup was slept on for years before it became a billion-dollar company.

Origin

Slang rooted in the metaphor of sleeping through an opportunity; became prevalent in hip-hop and internet culture by the 2000s

Fun Fact

Often used retrospectively to credit something that was good but lacked hype at the time.

Source: Definition backfill (hailey)