fifth wheel（牵引座）是什么意思？音标发音+图解场景

牵引座 /ˈfɪfθ ˈwiːl/ n

English: fifth wheel · 牵引座

释义：Coupling device enabling the tractor to be connected to the semitrailer and supporting its front portion.

这个词出现在以下图解场景（1）