Definition of "preconception"

preconception

noun
plural preconceptions
1. An opinion formed before obtaining adequate evidence, especially as the result of bias or prejudice.
  Quotations
  He told RAIL: "We had no preconceptions, but you would assume a newer train to have better air quality than an older one. We found that was not necessarily the case.
  2021 October 6, Paul Clifton, “Network News: RSSB research exposes poor air quality on diesel trains”, in RAIL, number 941, page 14
2. A prejudice that prevents rational consideration of an issue.
adjective
not comparable
1. (medicine) Preconceptional.