What term describes a concise summary of a film in one sentence?

The term that best describes a concise summary of a film in one sentence is "Log line." A log line succinctly encapsulates the essence of the film's story, often highlighting the main character, their goal, and the conflict they face. It serves as a quick pitch to grab the audience's attention and provide a clear understanding of the film's premise.

While a synopsis generally offers a more detailed summary of the plot, a tagline is typically a catchy phrase used in marketing to evoke interest, and an abstract conveys the overarching themes or study of a film, often used in academic contexts. Thus, the specificity and brevity of a log line make it the most fitting term for a one-sentence summary of a film.