noun
tipster; tout
A person who sells betting tips, especially in horse racing or other gambling contexts. Often carries a slightly shady or street-level connotation.
競馬場の近くでコーチ屋に声をかけられた。
I was approached by a tipster near the racetrack.
あのコーチ屋の予想はよく当たるらしい。
That tipster's predictions seem to be accurate.
Compound of コーチ (from English 'coach', here meaning a tip or advice in gambling contexts) and 屋 (a suffix for a shop or person engaged in a trade).