Definitions for "Peer-reviewed"
see refereed journal
journal articles are frequently referred to as "peer reviewed". This means that before an article is accepted for publication within a journal, it is first reviewed and corrected by a subject expert. Peer reviewed journal articles are typically considered of higher quality because of this review process than non-peer-reviewed journal articles.
Usually said of journals. Peer-reviewed journals only publish articles that have been approved by a panel of experts in a field of study. Some research projects require that you only use peer-reviewed sources.