Meaning of "B" Movie

a low-budget movie, especially (formerly) one made for use as a companion to the main attraction in a double feature.

B movie

B movie
n.
A movie produced on a low budget, originally made to accompany the main feature in a double billing. Also called B picture.

B picture

B picture n.
a low-budget mediocre film made esp. to accompany a major feature film on a double bill. Also called B movie.