The commonly accepted definition of a beamer is a fast full toss, passing dangerously near the striker's throat. The Laws of Cricket give a wider definition - a 'full pitched ball'. So, it doesn't have to be fast and it doesn't have to be at the throat to bring sanctions against the bowler

In judging whether a delivery is a beamer the umpire must decide the height at which the ball passes or would have passed the striker standing upright at the crease. For a slow delivery, the relevant height is shoulder height; for anything quicker, it is waist height. The 'would have passed' phrase means that the umpire's judgement is not to be influenced by either the batsman's position or posture or by whether he hits the ball. The direction is not a consideration, the ball might be delivered straight at the batsman or it might be several feet wide of him, its height is all that matters

A beamer might occur because either it has been bowled deliberately, or because the ball has slipped from the bowler's hand as he delivered it. Whether intentional or not, it can be very dangerous. The striker is not expecting it, often does not get a good sight of the ball and could quite easily be struck by it. If a bowler bowls several accidental beamers, it indicates that, for whatever reason - a wet ball, perhaps, or just simple incompetence - the bowler does not have sufficient control of the ball to be able to deliver it safely. The Law requires the umpire to call and signal No ball for each occurrence. On the first occasion he will caution the bowler, the second time give him a final warning and finally, after a third such ball, have him removed from the attack for the remainder of that innings.

The deliberate beamer, the attempt by the bowler to scare the daylights out of the striker or, worse, attempt to injure him, cannot be tolerated. It is highly dangerous, unfair and simply not cricket. If the umpire considers the beamer to have been bowled deliberately, there is to be no caution or warning. The bowler has bowled his last ball in that innings. He will be reported by the umpires to the appropriate authority who may well see to it that he has a lengthy enforced break from the game in which to contemplate his unsportsmanlike behaviour.