IPA: /ˈhɔːrsləs/
KK: /ˈhɔrs.ləs/
Not having a horse.
In the early 1900s, the term 'horseless carriage' was used to describe early automobiles.
Horseless → It is formed from "horse" (from Old English "hors", meaning a large domesticated animal used for riding and work) and "-less" (meaning without). The word "horseless" means without a horse, typically referring to a vehicle that does not require horses for propulsion, such as an automobile.
Think of being 'without' ('-less') a 'horse' — that's why horseless means lacking a horse.