ADVERB (2)

1. on the lower or downward side; on the underside of;
- Example: "a chest of drawers all scratched underneath"

2. under or below an object or a surface; at a lower place or level; directly beneath;
- Example: "we could see the original painting underneath"
- Example: "a house with a good foundation underneath"

The Collaborative International Dictionary of English v.0.48:

Underneath \Un`der*neath"\, adv. [OE. undirnepe. See Under,
   and Beneath.]
   Beneath; below; in a lower place; under; as, a channel
   underneath the soil.
   [1913 Webster]

         Or sullen mole, that runneth underneath. --Milton.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Underneath \Un`der*neath"\, prep.
   Under; beneath; below.
   [1913 Webster]

         Underneath this stone lie
         As much beauty as could die.             --B. Jonson.
   [1913 Webster]

WordNet (r) 3.0 (2006):

underneath
    adv 1: on the lower or downward side; on the underside of; "a
           chest of drawers all scratched underneath"
    2: under or below an object or a surface; at a lower place or
       level; directly beneath; "we could see the original painting
       underneath"; "a house with a good foundation underneath"

Moby Thesaurus II by Grady Ward, 1.0:

34 Moby Thesaurus words for "underneath":
   bed, bedrock, belly, below, beneath, bottom, bottom side, breech,
   buttocks, clandestine, covert, downside, fundament, furtive,
   hardpan, hole-and-corner, lower side, lowest layer, lowest level,
   neath, nether side, nethermost level, rock bottom, sole, stealthy,
   subordinate to, substratum, surreptitious, under, under-the-table,
   underbelly, undercover, underlayer, underside