Countable noun; chiefly British informal in one sense.
Definitions
a projector, especially one used for presentations or to display images on a screen We connected the laptop to the beamer before the meeting started.
in cricket, a ball bowled as a full toss at dangerous height, usually above the batsman's waist The umpire called the delivery a beamer and signaled a no-ball.
informal: a car with its headlights on full beam The beamer on the dark road blinded the drivers coming the other way.