slippage

Short definition from Wiktionary

Noun

1. 1
   The act of slipping, especially from a secure location.
2. 2
   The amount by which something has slipped.
3. 3
   A lessening of performance or achievement.
4. 4
   A decrease in motion, or in the power of a mechanical system, due to slipping.
5. 5
   The difference between estimated and actual transaction costs.
6. 6
   Movement of earth on a slope, a landslip.