Preconceptions are the ideas or opinions that you hold about something or someone before you actually have any experience of it / them. They are usually formed from a combination of other people telling you their experiences, and things you read / see on TV. They are often considered to be a bad thing.

Pre`con*cep"tion (?), n.

The act of preconceiving; conception or opinion previously formed.

 

© Webster 1913.