What a bad winner does

• Rejoices, in a smug way
• Eschews modesty
• Is smugly happy
• Rejoices, in an in-your-face manner
• Revels in victory
• Rejoices tactlessly
• Acts like a sore winner
• Is a bad winner
• Acts smug

Wiktionary Word definitions in Wiktionary
n. (plural of gloat English) vb. (en-third-person singular of: gloat)