|a black extremely hard inert substance having a high capture cross section for thermal neutrons. It is used as an abrasive and refractory and in control rods in nuclear reactors. Formula: B4C|
|an arrangement of five objects, as trees, in a square or rectangle, one at each corner and one in the middle.|
|a children's mummer's parade, as on the Fourth of July, with prizes for the best costumes.|
(B4C), crystalline compound of boron and carbon. It is an extremely hard, synthetically produced material that is used in abrasive and wear-resistant products, in lightweight composite materials, and in control rods for nuclear power generation
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