|Think Tank robot|
Artificial intelligence (or computer intelligence) is a term used in the fields of cybernetics, computer science, and related disciplines, to describe computer hardware and software sophisticated enough to reason independently, form new conclusions, and alter its own responses.
The android Data, built in the early 24th century, may be an example of a true artificial intelligence according to this definition. (TNG: "Encounter at Farpoint") So might certain other androids, notably, Ruk, an artifact of the Old Ones of Exo III. (TOS: "What Are Little Girls Made Of?") Data was equipped by his creator, Noonian Soong, with a positronic brain, based on an advanced neural-net design. He was eventually deemed an independent lifeform, with the rights and responsibilities of other life, lending weight to the notion that he qualifies as an artificial intelligence. (TNG: "The Measure Of A Man")
Most of the computer systems in use by the Federation and similar powers would probably not qualify; they are very powerful, but nevertheless remain essentially data storage, retrieval, and coordination devices.
Even certain highly advanced alien computers may or may not meet the criteria for artificial intelligence. Landru ruled Beta III for almost 6,000 years, but Kirk and Spock deduced its nature in less than a day. (That its subjects did not is probably a consequence of the near reverence in which they held Landru.) (TOS: "The Return of the Archons")