trailer
n. countablen. a short video that shows parts of a movie or show to get people excited to watch it. It can also mean a vehicle without an engine that is pulled by a car or truck.
n. a series of excerpts from a film or television programme used for promotional purposes. Also refers to an unpowered vehicle designed to be towed by another.
I saw a trailer for the new movie today.
The studio released a two-minute trailer to build anticipation for the summer blockbuster.
While the trailer successfully captured the film's visual grandeur, some critics argued it revealed too much of the plot, effectively spoiling the third act for prospective viewers.
From trail + -er. The film sense derives from the fact that previews were formerly shown after the main feature, rather than before as is usual today, that is trailing after the main feature.
In a computing context, refers to data at the end of a block or file that contains control information.