underlay

To lay (something) underneath something else; to put under.

To provide a support for something; to raise or support by something laid under.

“to underlay a cut, plate, or the like, for printing”

To put a tap on (a shoe).

(of a vein, fault, or lode) To incline from the vertical.

To lie in a position directly beneath.

To lie under or beneath.

“A stratum of clay underlies the surface gravel.”

To serve as a basis of; form the foundation of.

“a doctrine underlying a theory”

To be subject to; be liable to answer, as a charge or challenge.

To underlay.

A layer (of earth, etc.) that lies under another; substratum.

A soft floor covering that lies under a carpet.

Anything that is underlaid.

A piece of paper pasted under woodcuts, stereotype plates, etc. in a form, to bring them up to the necessary level for printing.

Lyrics; or more specifically, the way in which lyrics are assigned to musical notes.

“The underlay in bar 3 is unclear in Handel's manuscript.”