Boastful means forever talking about how good you are. Every conversation finds its way back to the same subject.
It is a criticism and a fairly old-fashioned one, and it suits children's stories and moral tales. The verb boast is far commoner in speech, and English also uses it neutrally about places and things, since a hotel can boast three restaurants without anybody objecting. Bragging is the informal version, and boastfulness is the noun. Modesty is the virtue this word is measured against.
1adjectiveboastfulShowing excessive pride in your own achievements.
“He was boastful about every deal he had ever done.”
Middle English
bostful
English, today
boastful
From Middle English bostful, equivalent to boast + ful.
Etymology from Wiktionary, CC BY-SA