s. In IMDB
parlance, a goof is an error
which can be detected by viewing the offending movie
or television show.
The presence of goofs in a film does little more than provide fodder for self-important continuity fascists and reinforces the notion that anyone who watches movies on a regular basis needs to get a life*.
Some of the more amusing goofs include things like mysterious costume changes mid-scene, visible boom mikes, and reflections of crew members in mirrors, glass, and water.
Clearly, the methodical hunting down of these callous transgressions against Art is a moral imperative, but try not to share your knowledge during a movie...especially those showing in a theater...where people near you might not want to notice the yellow Ked left dead-center in the samurai's feudal mansion.
* I should mention that I occasionally notice these things, and even point them out from time to time, but only when they seem pertinent. If you feel this smacks of hypocrisy, please mail $1 to me and I will consider apologizing.