Hudson River alligator

Hudson River alligator
 n.— «The quaint wooden pilings you see at the edge of Manhattan, the ones that trace the outlines of long-gone piers, are a hazard in the making. When a storm knocks one of them loose, the resultant floater—a “Hudson River alligator”—becomes a twenty-foot battering ram.» —“Secrets of the Deep” by Christopher Bonanos New York Magazine May 10, 2009. (source: Double-Tongued Dictionary)