French drain

Short definition from Wiktionary

Noun

1. 1
   A shallow trench, sometimes lined with tile or containing a perforated pipe, backfilled with gravel and then covered over, used to collect and channel runoff water.
2. 2
   A gravel-filled corridor with a perforated pipe running through it that runs against the foundation footings of a building, used to collect ground water and drain it away from the building's interior.