1beam 
/ˈbi:m/ noun
plural beams /ˈbi:m/ noun [count] 1 a : a line of light coming from a source (such as the sun or a headlight)
▪ a bright beam of light ▪ We saw the beams from their flashlights. ▪ a laser beam — see also high beam, low beam, sunbeam
b : a line of energy, particles, etc., that cannot be seen
▪ a beam of electrons ▪ X-ray beams 2 : a long and heavy piece of wood or metal that is used as a support in a building or ship
▪ the building's steel support beams ▪ wood ceiling beams — see also balance beam
▪ a bright beam of light ▪ We saw the beams from their flashlights. ▪ a laser beam — see also high beam, low beam, sunbeam
b : a line of energy, particles, etc., that cannot be seen
▪ a beam of electrons ▪ X-ray beams
▪ the building's steel support beams ▪ wood ceiling beams — see also balance beam
off beam
Brit, informal : incorrect or mistaken
▪ My guess was way off beam. [=(US) off base]
▪ My guess was way off beam. [=(US) off base]
on the beam
informal : exactly correct
▪ His description of the problem was right on the beam. [=(more commonly) on the mark]
▪ His description of the problem was right on the beam. [=(more commonly) on the mark]
— beamed adjective
▪ The living room has a beamed ceiling. [=a ceiling that is supported with wood or metal beams]
▪ The living room has a beamed ceiling. [=a ceiling that is supported with wood or metal beams]
