dead weight

Short definition from Wiktionary

Noun

1. 1
   Unremitting heavy weight that does not move.
2. 2
   The largest weight of cargo a ship is able to carry; i.e., the weight of a ship when fully loaded minus its weight when empty.
3. 3
   A dead load.
4. 4
   That which is useless or excess; that which slows something down.
5. 5
   The total (unpowered) weight of a train to be propelled (or hauled) by the locomotive; another locomotive being hauled dead as part of the train is a dead weight.

Adverb

1. 1
   With just enough weight for a ball to drop into a pocket, or come to rest in a precisely determined position.