intelligence quotient

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A number seen as a measure of a person's intelligence, usually representing the person's score on an intelligence test as expressed in relation to the scores of others who have taken the same test, with the average score set at 100.
• noun The ratio of tested mental age to chronological age, usually expressed as a quotient multiplied by 100. No longer in scientific use.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A score derived from one of several different standardized tests attempting to measure intelligence.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a measure of a person's intelligence as indicated by an intelligence test; the ratio of a person's mental age to their chronological age (multiplied by 100)