operational definition

An operational definition is a showing of something—such as a  variable, term, or object—in terms of the specific  process or set of validation tests used to determine its presence and quantity. Properties described in this manner must be publicly accessible so that persons other than the definer can independently measure or test for them at will. An operational definition is generally designed to model a conceptual definition.
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a concrete and procedural definition of something that is otherwise difficult to agree about.  For example, people can disagree about how creative a particular person is. After all, people are creative in different ways and what one person would consider "creative" another person might consider "off the wall."  But an operational definition removes the challenge of differing opinions and ties the definition to a procedure that is precise and, for those using the operational definition, not contestable.  A set of questions might be used to "operationally define" creativity, for example so that every time someone answered a question "yes" they were given a point.  Their operationally defined creativity might be the sum of all their points -- even if the questions have nothing to do with what you and I ordinarily think of "creativity."  Questions about whether the operational definition measures what it says it measures are questions about the "validity" of an operational definition.  One can have an operational definition without it being "valid."