WordNet (r) 3.0 (2006):

upper bound
    n 1: (mathematics) a number equal to or greater than any other
         number in a given set

The Free On-line Dictionary of Computing (30 December 2018):

upper bound

   An upper bound of two elements x and y under some relation
   <= is an element z such that x <= z and y <= z.

   ("<=" is written in LaTeX as \sqsubseteq).

   See also least upper bound.

   (1995-02-15)