The American use of this term comes from a 1979 movie called "The Psychotronic Man". It refers to the ability to control the physical world with your mind. Because of this movie the word psychotronic fell into generic usage for obscure cult films.
The practice of any type of trump or trumping action where something is being done by someone or a group of others in such a way as to conquer, overcome, outwit, beat, defeat, surpass, outshine, do better, or bring betterment to someone, a group, or some thing.
The cavalry troops chose to study the use of psychotrumpics instead of hand to hand combat to overcome the enemy.
The practice of using a card game strategy to psychologically trump an opponent by use of a trick or a better move, or being shrewder in playing the cards in hand.
The champion card player was famous for using psychotrumpic strategies to outwit his opponents.