transitive verb underlaid -·laid′, underlaying -·lay′·ing

1. to cover, line, or extend over the bottom of the leather is underlaid with felt
2. to lay (something) under something else, esp. as a support, wedge, etc.
3. to raise or support with something laid underneath the roof must be underlaid with trusses
4. Printing to provide with an underlay

Etymology: ME underlein < OE underlecgan

noun

1. something laid underneath
2. Printing a patch or patches of paper laid under type, cuts, etc. to raise the level of the face