1. To writhe, flail, or fling around wildly, violently, or uncontrollably. One of the cables came loose in the wind and lashed around across the deck of the boat. The toddler started lashing around in the midst of his tantrum.
2. To swing or flail something around wildly, violently, or uncontrollably. In this usage, a noun or pronoun is used between "lash" and "around." The lion tamer lashed his whip around to impress the audience. The wind lashed the flag around all night long, but it never came unfixed from the flagpole.