Meaning of upper bound

up'per bound'

Pronunciation: [key]
— Math. Math.
  1. an element greater than or equal to all the elements in a given set: 3 and 4 are upper bounds of the set consisting of 1, 2, and 3. Cf. (def. 4),
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.