rule out

Collins Concise English Dictionary © HarperCollins Publishers::

rule out verb (tr, adverb)

1. to dismiss from consideration
2. to make impossible; preclude or prevent

WordReference Random House Learner's Dictionary of American English © 2025

rule /rul/   n., v., ruled, rul•ing. 
n. 

1. a principle guiding how one behaves, the way things are done, etc.:
   [countable] a rule in hockey saying to eject anyone fighting.
2. the customary occurrence, practice, etc.;
   the normal way something is done:
   [countable] Her being late is the rule rather than the exception.
3. government;
   amount of time ruling:
   [uncountable] in the days of foreign rule.
4. [countable] the code of regulations observed by a religious congregation.
5. Weights and Measures ruler (def. 2).

v. 

6. to use power, authority, or influence over: [~ + object]
   to rule a kingdom.
   [no object]
   to rule for only a decade.
7. to decide in a court of law or by some authority;
   decree: [no object]
   How will the court rule?
   [~ + on + object]
   The court will rule on the matter at its next session.
   [~ + (that) clause]
   The court ruled that she could not keep her baby.
8. to mark with lines, esp. parallel straight lines, with the aid of a ruler:
   [~ + object] to rule paper.
9. [~ + object] to be superior in (a group), so as to hold influence over.
10. to influence or control:
    [~ + object] sometimes ruled by passion and not by logic.
11. rule out, to eliminate from thinking about;
    to decide to ignore: [~ + out + object]
    We can rule out the possibility of an overnight improvement in the economy.
    [~ + object + out]
    We can't rule it out completely.

Idioms

12. Idioms as a rule, generally;
    usually:
    He's there by 7:30 as a rule.

WordReference Random House Unabridged Dictionary of American English © 2025

rule (ro̅o̅l),  n., v., ruled, rul•ing. 

n. 

1. a principle or regulation governing conduct, action, procedure, arrangement, etc.:
   the rules of chess.
2. the code of regulations observed by a religious order or congregation:
   the Franciscan rule.
3. the customary or normal circumstance, occurrence, manner, practice, quality, etc.:
   the rule rather than the exception.
4. control, government, or dominion:
   under the rule of a dictator.
5. tenure or conduct of reign or office:
   during the rule of George III.
6. a prescribed mathematical method for performing a calculation or solving a problem.
7. Weights and Measures ruler (def. 2).
8. Astronomy (cap.) the constellation Norma.
9. Printing a thin, type-high strip of metal, for printing a solid or decorative line or lines.
10. Law
    • Law a formal order or direction made by a court, as for governing the procedure of the court (general rule) or for sending the case before a referee (special rule.)
    • a legal principle.
    • a court order in a particular case.
11. Law rules, [Penol.] (formerly)
    • a fixed area in the neighborhood of certain prisons within which certain prisoners were allowed to live.
    • the freedom of such an area.
12. [Obs.] behavior.
13. as a rule, generally;
    usually:
    He arrives at eleven o'clock, as a rule.

v.t. 

14. to control or direct;
    exercise dominating power, authority, or influence over;
    govern:
    to rule the empire with severity.
15. to decide or declare judicially or authoritatively;
    decree:
    The judge ruled that he should be exiled.
16. to mark with lines, esp. parallel straight lines, with the aid of a ruler or the like:
    to rule paper.
17. to mark out or form (a line) by this method:
    to rule lines on paper.
18. to be superior or preeminent in (a specific field or group);
    dominate by superiority;
    hold sway over:
    For centuries, England ruled the seas.

v.i. 

19. to exercise dominating power or influence;
    predominate.
20. to exercise authority, dominion, or sovereignty.
21. to make a formal decision or ruling, as on a point at law.
22. to be prevalent or current:
    Higher prices ruled throughout France.
23. rule out:
    • to prove to be unrelated or not for consideration;
      eliminate;
      exclude:
      to rule out the possibility of error.
    • to make impossible or impracticable:
      The rainstorm ruled out the holiday camping.
24. rule the roost. See roost (def. 4).

• Late Latin rēgulāre, derivative of rēgula
• Old French riuler, rieuler, ruler
• Latin rēgula straight stick, pattern (see regula); (verb, verbal) Middle English riwlen, reulen, rewellen
• Old French riule
• (noun, nominal) Middle English riule, reule 1175–1225

Synonyms

• 1. standard, law, ruling, guide, precept, order. See principle. 
• 4. command, domination, mastery, sway, authority, direction.
• 14. Rule, administer, command, govern, manage mean to exercise authoritative guidance or direction.
  Rule implies the exercise of authority as by a sovereign:
  to rule a kingdom.
  Administer places emphasis on the planned and orderly procedures used:
  to administer the finances of an institution.
  Command suggests military authority and the power to exact obedience; to be in command of:
  to command a ship.
  To govern is authoritatively to guide or direct persons or things, esp. in the affairs of a large administrative unit:
  to govern a state.
  To manage is to conduct affairs, i.e., to guide them in a unified way toward a definite goal, or to direct or control people, often by tact, address, or artifice:
  to manage a business.
• 15. order, judge.