Green’s Dictionary of Slang

trap n.2

[abbr. rattletrap n. (2)]

1. [19C] a small, sprung, two-wheeled carriage, a gig.

2. [1930s–60s] (US) a dilapidated old car.

In phrases

hot trap (n.) [hot adj. (5d)]

[1930s–50s] (US Und.) a stolen car .