Systematic

Antonyms of systematic:
unsystematic, chaotic, disordered, disorderly, shambolic, unordered, disorganized, haphazard, hit-or-miss, immethodical, irregular, nonsystematic, patternless, planless, systemless.
Examples of usage:
  1. Some of the teachers, so far as I can judge, quite sympathize with the boys, not only in their ends but in their methods; some think it their moral duty to urge deliberate action and try to make the students as organized and systematic as possible, and some take the good old Chinese ground that there is no certainty that any good will come of it.
    "Letters from China and Japan", John Dewey Alice Chipman Dewey.
  2. There was no systematic study of instrumental composition.
    "Some Forerunners of Italian Opera", William James Henderson.
  3. In my last annual message I recommended that Congress authorize the appointment of a commission for the purpose of making systematic investigations with reference to the cause and prevention of yellow fever.
    "Complete State of the Union Addresses from 1790 to the Present", Various.