Longman Dictionary of Contemporary English
Wiktionary
n. 1 A component that is part of a larger construction, such as a brick or a stone. 2 A block made of wood or plastic that is used as a children's toy.
WordNet
n. a single undivided natural thing occurring in the composition of something else; "units of nucleic acids" [syn: unit]
a block of material used in construction work
Usage examples of "building block".
There were lots of ways to make crystal structures out of the silicon anion, the fundamental silicon-oxygen tetrahedral building block.
He had the com center patch him through on a phone line and in a half-hour-long conversation he told the assistant chief every step he had taken and described every building block of evidence that led to the arrest.
The process involves the isolation and comparison of fragments of DNA-deoxyribonucleic acid-the basic building block of the chromosome.
Our second key technological building block was the Langston Field, which absorbs and stores energy in proportion to the fourth power of incoming particle energy: that is, a slow-moving object can penetrate it, but the faster it's moving (or hotter it is) the more readily it is absorbed.