The Skeptic's Dictionary is a collection of cross-referenced skeptical essays by Robert Todd Carroll, published on his website skepdic.com and in a printed book. The skepdic.com site was launched in 1994 and the book was published in 2003 with nearly 400 entries. As of January 2011 the website has over 700 entries. A comprehensive single-volume guides to skeptical information on pseudoscientific, paranormal, and occult topics, the bibliography contains some seven hundred references for more detailed information. According to the back cover of the book, the on-line version receives approximately 500,000 hits per month.

Scientific skepticism or rational skepticism, sometimes referred to as skeptical inquiry, is a position in which one questions the veracity of claims lacking empirical evidence. In practice, the term most commonly refers to the examination of claims and theories that appear to be beyond mainstream science, rather than the routine discussions and challenges among scientists. Scientific skepticism differs from philosophical skepticism, which questions humans' ability to claim any knowledge about the nature of the world and how they perceive it, and the similar but distinct methodological skepticism, which is a systematic process of being skeptical about the truth of one's beliefs.