What is "star height"

n. (context computing theory English) A measure of the structural complexity of a regular expression, equal to the maximum nesting depth of stars in the expression.

In theoretical computer science, more precisely in the theory of formal languages, the star height is a measure for the structural complexity of regular expressions: The star height equals the maximum nesting depth of stars appearing in the regular expression. The concept of star height was first defined and studied by Eggan (1963).