underseal

noun
  1. a coating of a tar or rubber-based material applied to the underside of a motor vehicle to retard corrosionUS name: undercoat
verb
  1. (tr) to apply a coating of underseal to (a motor vehicle)
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012