We don't have synonyms for undersealing yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are underdealing, underselling and underfeeling.
(n) :
A thick, resilient coating applied to the underbody or chassis of an automobile to protect against damage from small stones, etc, which would rapidly chip ordinary paint and allowing rusting to begin.
(v) :
(transitive) To coat (the underbody or chassis of a vehicle) with underseal.
(n) :
A thick, resilient coating applied to the underbody or chassis of an automobile to protect against damage from small stones, etc, which would rapidly chip ordinary paint and allowing rusting to begin.
(v) :
(transitive) To coat (the underbody or chassis of a vehicle) with underseal.