IPA: /ˈhɔːrspleɪər/
KK: /ˈhɔrsˌpleɪər/
A person who frequently places bets on horse races.
The horseplayer studied the statistics before placing his bets.
Horseplayer → It is formed from "horse" (from Old English "hors", meaning a large domesticated animal used for riding and work) and "player" (from Old French "pleier", meaning one who plays). The word "horseplayer" refers to a person who participates in betting on horse races or engages in activities related to horse racing.
Think of someone who is involved in 'playing' or betting on 'horses' — that's what a horseplayer does.
No commonly confused words.