[pay dirt] {n.}, {slang}
1. The dirt in which much gold is found.
* /The man searched for gold many years before he found pay dirt./
2. {informal} A valuable discovery. — Often used in the phrase "strike pay dirt".
* /When Bill joined the team, the coach struck pay dirt./* /Jean looked in many books for facts about her hometown, and finally she struck pay dirt./
Compare: STRIKE IT RICH.