Deviation meaning : The act of deviating; wandering off the correct or true path or road A departure from the correct way of acting The state or result of having deviated; a transgression; an act of sin; an error; an offense. (contract law) The voluntary and unnecessary departure of a ship from, or delay in, the regular and usual course of the specific voyage insured, thus releasing the underwriters from their responsibility. (Absolute Deviation) The shortest distance between the center of the target and the point where a projectile hits or bursts. For interval variables and ratio variables, a measure of difference between the observed value and the mean. The signed difference between a value and its reference value.