underrun

(ŭnˌdər-rŭnˈ)

1. To run, pass, or go beneath.
2. Nautical To haul (a line or cable) onto a boat for inspection or repair.

1. Something that runs under, as:
   a. An amount or a quantity produced that is less than what has been estimated.
   b. The difference between this amount or quantity and what has been estimated.
2. An undercurrent.