underflows

/AH1 N D ER0 F L OW0 Z/
noun
  1. 1

    A current flowing below the surface.

  2. 2

    A condition in which the value of a computed quantity is smaller than the smallest non-zero value that can be physically stored; usually treated as an error condition

  3. 3

    The error condition that results from an attempt to retrieve an item from an empty stack

Source: https://en.wiktionary.org/wiki/underflow, https://en.wiktionary.org/wiki/underflows