The application or employment of a process or feature by which an artist will ensure both the ratio AND perspective of an image remain relative to that of the original image. Failure to "constrain proportions" has resulted in many innocent men being "duped" on internet dating sites (and the like), sustaining an eternal loss of essential "crop points."
TA:"I'm tryin to photoshop that sikk pic you got of me killin' a keg stand at the Rutgers party, Nig." "Everytime I resample, I end up lookin like Nicole Richie doin' a headstand on a Heineken keg can."
RA:"You need to constrain proportions"
....Beware the rubber bakk