What does PSI stand for in relation to tire pressure?

The abbreviation PSI, when related to tire pressure, stands for "Pounds per Square Inch." This unit measures the amount of pressure exerted by the air inside the tire against the tire's inner walls. It quantifies how much force is being applied in a specific area—hence the term pounds per square inch, which conveys the pressure expressed in pounds over an area measured in square inches. Understanding PSI is crucial for maintaining optimal tire pressure, which significantly impacts vehicle handling, fuel efficiency, and overall safety.

The other options do not accurately reflect the standard terminology used in automotive contexts; for instance, pounds per square foot and pounds of surface indicator are not terms related to tire pressure. Furthermore, the term "Pressures Involutionary System" does not exist in automotive language. Therefore, "Pounds per Square Inch" is the correct and widely accepted definition associated with tire pressure measurement.