COUNTERFACTUAL
counterfactual, contrary to fact
(adjective) going counter to the facts (usually as a hypothesis)
Source: WordNet® 3.1
Etymology
Adjective
counterfactual
Contrary to the facts; untrue.
Of or in comparison to a hypothetical state of the world.
Noun
counterfactual (plural counterfactuals)
A claim, hypothesis, or other belief that is contrary to the facts.
A hypothetical state of the world, used to assess the impact of an action.
(philosophy) A conditional statement in which the conditional clause is false, as "If I had arrived on time . . .".
Source: Wiktionary