noun pl. ideologies -·gies

1. Archaic the study of the nature and origin of ideas
2. thinking or theorizing of an idealistic, abstract, or impractical nature; fanciful speculation
3. the doctrines, opinions, or way of thinking of an individual, class, etc.; specif., the body of ideas on which a particular political, economic, or social system is based

Etymology: Fr idéologie: see ideo- & -logy