fifty PSI finger noun (among Canadian armed forces personnel) a finger poked into someone’s chest to emphasise a point forcefully CANADA
The “fifty-p.s.i. finger” is an index finger that is jabbed angrily into another’s chest, to punctuate points in an argument. The finger is said to have a pressure of about 50 pounds per square inch. — Tom Langeste, WordsontheWing, p. 96, 1995