frozen chicken head
n.— «Hard ski surfaces come in many forms, from “boilerplate” or “bulletproof” after a January thaw/freeze (Vermont natives like to say the snow “toightened up” after the thaw) to “frozen chicken heads,” when spring slush refreezes overnight.» —“Ice advice: how to handle the hard cases” by Bill Kerig, Eric Deslauriers, Lito Tejada-Flores, Harald Harb Skiing Feb. 1, 1998. (source: Double-Tongued Dictionary)