Sentence:  He heaved the bag and its contents over the lip of the <WSD>boot</WSD> and on to the flagstones. When it was out, no longer in that <WSD>boot</WSD> but on the ground, and the bag was still intact, he knew the worst was over. 
Meaning of the word marked with <WSD> tags:  The luggage storage compartment of a sedan or saloon car.