bəˈrilēəm noun
( -s )
Etymology: New Latin, from Greek bēryllion, diminutive of bēryllos beryl — more at beryl
: a steel-gray light strong brittle toxic bivalent metallic element having high electric conductivity and high permeability to X rays that occurs in combination (as in beryl, chrysoberyl, and phenakite), that is produced by reduction of its compounds (as by electrolysis), and that is used chiefly as a hardening agent in alloys (as with copper), as windows in X-ray tubes, and as a moderator and reflector in nuclear reactors — symbol Be ; called also glucinium ; see element table