IPA: //fɔːrˈstɔːlər//
KK: /fɔrˈstɔlər/
A person who prevents something from happening by taking action in advance, often by buying goods before they are available to others to increase their value.
The forestaller bought all the tickets before they went on sale to resell them at a higher price.
Forestaller → It is formed from "fore-" (meaning before) and "stall" (from Old English *stallan*, meaning to stop or delay). The word "forestaller" refers to someone who stops or delays something before it happens.
Think of someone who acts "before" ("fore-") something happens to "stop" ("stall") it — that's why a forestaller is someone who prevents something from occurring.