Nouns

(n)carpet pad, rug pad, underlay, underlaymenta pad placed under a carpet

Verbs

(v)underlayraise or support (the level of printing) by inserting a piece of paper or cardboard under the type“underlay the plate”
(v)underlayput (something) under or beneath“They underlaid the shingles with roofing paper”
(v)underlayprovide with a base, support, lining, or backing“underlay the boards with joists”