the.com/fastback

means A car body style where the roofline slopes in one continuous, unbroken line from the roof down to the rear bumper, rather than stepping down to a separate trunk.

from Straightforward compound coinage from 'fast' + 'back,' arising in early-to-mid 20th-century automotive design language — 'fast' here borrowed from the streamlining sense (as in 'fastness' of aerodynamic shape) rather than speed itself, paired with 'back' for the car's rear profile. It joined a small family of descriptive body-style terms, alongside 'notchback' and 'hatchback,' coined by engineers and marketers to name silhouettes as cars evolved from boxy carriages into streamlined shapes.