[1] : WordNet (r) 2.0

building block
     n 1: a single undivided natural thing occurring in the
          composition of something else; "units of nucleic acids"
          syn: unit
     2: a block of material used in construction work
see also:
unit 

[2] : Moby Thesaurus II by Grady Ward, 1.0

52 moby thesaurus words for "building block":
   air, atom, atomic particles, atoms, brute matter, chemical element,
   component, constituent, core, distillate, distillation, earth,
   element, elementary particle, elementary unit, elixir, essence,
   fabric, fire, fundamental particle, gist, heart, hyle, hypostasis,
   kernel, marrow, material, material world, materiality, matter,
   meat, medium, molecule, monad, natural world, nature, nub,
   physical world, pith, plenum, quintessence, sap, soul, spirit,
   stuff, substance, substratum, sum and substance, tangible,
   the four elements, unit of being, water

Building Block >> B Words
Building Block, definition of term: Building Block
building+block_pag1.html

Building >> B Words
Building, definition of term: Building
building_pag1.html

Block >> B Words
Block, definition of term: Block
block_pag1.html

Block Out >> B Words
Block Out, definition of term: Block Out
block+out_pag1.html

Block Grant >> B Words
Block Grant, definition of term: Block Grant
block+grant_pag1.html

Block Letter >> B Words
Block Letter, definition of term: Block Letter
block+letter_pag1.html

Gin Block >> G Words
Gin Block, definition of term: Gin Block
gin+block_pag1.html

Cinder Block >> C Words
Cinder Block, definition of term: Cinder Block
cinder+block_pag1.html

Office Block >> O Words
Office Block, definition of term: Office Block
office+block_pag1.html

Block And Tackl >> B Words
Block And Tackl, definition of term: Block And Tackl
block+and+tackl_pag1.html