Definition 1 - Encouragement / Motivational Beasting
A group or individuals are pushed to their limits or to see how far they go before they jack. Not always nice to watch and a real bummer if you are the beastee.
One reason for Beasting is to make sure that the person or group will be able to carry out a harder than usual task and it sorts the men from the boys.
A group that has been beasted and survived will have developed a comradeship between them, morale will be high.
Beasting or to beast is probably not PC in the Forces anymore.
One who administers the Beasting is known as a Beast Master.
Definition 2 - Punishment Beasting
A punishment ritual, usually involving physical violence to some degree but can be verbal, carried out by one or more persons and used to intimidate or reinforce hierarchical status within a group. Can be anything from a Regimental Bath to a good shoeing.
Beastings do not go on in today's Armed Forces of Her Majesty.....much.