rule out

Collins Concise English Dictionary © HarperCollins Publishers::

rule out vb (transitive, adverb)

rule n., v., ruled, rul•ing.
n.

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

to use power, authority, or influence over: [~ + object]to rule a kingdom.[no object]to rule for only a decade.
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.
to mark with lines, esp. parallel straight lines, with the aid of a ruler:[~ + object]to rule paper.
[~ + object] to be superior in (a group), so as to hold influence over.
to influence or control:[~ + object]sometimes ruled by passion and not by logic.
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

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

rule n., v., ruled, rul•ing.

a principle or regulation governing conduct, action, procedure, arrangement, etc.:the rules of chess.
the code of regulations observed by a religious order or congregation:the Franciscan rule.
the customary or normal circumstance, occurrence, manner, practice, quality, etc.:the rule rather than the exception.
control, government, or dominion:under the rule of a dictator.
tenure or conduct of reign or office:during the rule of George III.
a prescribed mathematical method for performing a calculation or solving a problem.
Weights and Measuresruler (def. 2).
Astronomy(cap.) the constellation Norma.
Printinga thin, type-high strip of metal, for printing a solid or decorative line or lines.
Law
- Lawa 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.
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.
[Obs.]behavior.
as a rule, generally;
usually:He arrives at eleven o'clock, as a rule.

v.t.

to control or direct;
exercise dominating power, authority, or influence over;
govern:to rule the empire with severity.
to decide or declare judicially or authoritatively;
decree:The judge ruled that he should be exiled.
to mark with lines, esp. parallel straight lines, with the aid of a ruler or the like:to rule paper.
to mark out or form (a line) by this method:to rule lines on paper.
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.

to exercise dominating power or influence;
predominate.
to exercise authority, dominion, or sovereignty.
to make a formal decision or ruling, as on a point at law.
to be prevalent or current:Higher prices ruled throughout France.
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.
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