What is considered praying a rosary; is it once around the beads (five decades) or fifteen times around the beads?

Praying the rosary normally means praying all five decades of one of the four sets of mysteries: the joyful, luminous, sorrowful or glorious mysteries. So that would be five decades or “once around the beads.” Of course, one could simply pray a decade or two, or, time permitting, all four sets of the rosary mysteries comprising twenty decades.