Wiktionary
three-peat
n. (context US slang English) A third successive win. vb. (context US slang English) To win somethings three times consecutively.
Wikipedia
Three-peat
Three-peat is a term used primarily in American sports to refer to winning three consecutive championships. The term, a portmanteau of the words three and repeat, originated with the Los Angeles Lakers of the National Basketball Association, during their unsuccessful campaign for a third consecutive championship during the 1988–89 season. The term is a registered trademark owned by Pat Riley, the Lakers' head coach from 1981–1990, although it was coined by L.A. player Byron Scott immediately after their victorious championship defense against the Detroit Pistons in the 1988 NBA Finals.