short subject vs movie

short subject and movie both are nouns.

Word	Noun	Adjective	Verb	Adverb
short subject	Yes	No	No	No
movie	Yes	No	No	No

As nouns, movie is a hypernym of short subject; that is, movie is a word with a broader meaning than short subject:

short subject: a brief film; often shown prior to showing the feature
movie: a form of entertainment that enacts a story by sound and a sequence of images giving the illusion of continuous movement

short subject (noun)	movie (noun)
a brief film; often shown prior to showing the feature	a form of entertainment that enacts a story by sound and a sequence of images giving the illusion of continuous movement