underlayment

[ uhn-der-ley-muh nt ]
/ ˌʌn dərˈleɪ mənt /

noun

material laid between a subfloor and a finish floor of linoleum, asphalt tile, etc.

Origin of underlayment

First recorded in 1945–50; underlay + -ment
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019