This term defines the practise of analysing large volumes of data, seeking possible relationships without any pre-defined hypothesis or goal. 

This practise is sometimes employed when working with 'big data' and often leads to premature conclusions. When working with big data, it is very easy to find statistically significant results, but it is much harder to spot if those results are actually meaningful, especially without a specific hypothesis. 

Data dredging is sometimes described as "seeking more information from a dataset than it actually contains" (CASRAI).