undercoating
noun
un·der·coat·ing ˈən-dər-ˌkō-tiŋ 
: a usually asphalt-based waterproof coating applied to the underside of a vehicle
Example Sentences
Recent Examples on the Web And the Winner of the Inker: Gypsum: The primary ingredient in car undercoating. 
Pat Myers, Washington Post, 21 July 2022 Down is a fluffy cluster that comes from the undercoating of the bird, down pillows are known for their soft cloud-like feel. Jamie Kim, Good Housekeeping, 18 Feb. 2021 Down is a fluffy undercoating cluster, whereas feathers are flatter with quills and come from the bird’s outer covering. Jamie Kim, Good Housekeeping, 18 Feb. 2021 Even undercoating can trap the brine, which, upon drying, can attract future moisture. Bob Weber, chicagotribune.com, 8 Nov. 2019 Sparks thrown up as the rail cars and autos skidded along the pavement had ignited the tires and undercoating of the cars. John Kelly, Washington Post, 6 Jan. 2018 In summer, the huge, compound green leaves glow with an undercoating of golden indumentum, and in fall, long, fuzzy wands produce airy sprays of tiny white flowers. Ciscoe Morris, The Seattle Times, 9 Aug. 2017 See More
Pat Myers, Washington Post, 21 July 2022 Down is a fluffy cluster that comes from the undercoating of the bird, down pillows are known for their soft cloud-like feel. Jamie Kim, Good Housekeeping, 18 Feb. 2021 Down is a fluffy undercoating cluster, whereas feathers are flatter with quills and come from the bird’s outer covering. Jamie Kim, Good Housekeeping, 18 Feb. 2021 Even undercoating can trap the brine, which, upon drying, can attract future moisture. Bob Weber, chicagotribune.com, 8 Nov. 2019 Sparks thrown up as the rail cars and autos skidded along the pavement had ignited the tires and undercoating of the cars. John Kelly, Washington Post, 6 Jan. 2018 In summer, the huge, compound green leaves glow with an undercoating of golden indumentum, and in fall, long, fuzzy wands produce airy sprays of tiny white flowers. Ciscoe Morris, The Seattle Times, 9 Aug. 2017 See More Word History
First Known Use
1922, in the meaning defined above