IPA: /ˈɡloʊtər/
KK: /ˈɡloʊtər/
A person who takes pleasure in their own success or someone else's misfortune, often showing it in a smug or boastful way.
After winning the game, he became a gloater, bragging about his victory to everyone.
Gloater → It is formed from "gloat" (from Middle English *gloten*, meaning to look at with great pleasure) and "-er" (meaning a person who). A gloater is a person who looks at something with great pleasure, often in a smug or self-satisfied way.
Think of someone who takes great pleasure in looking at their own success or someone else's misfortune — that's what a gloater does.