A momentary reversal of refrigerant flow through the compressor when the lift exceeds what the impeller can make at that flow, repeating until conditions change
Used across 4 Anvilfield field guides, most in HVAC.
Also defined as
Flow reversal in a centrifugal compressor at low load and high lift; damaging and centrifugal-only
Flow reversal in a centrifugal at too little flow or too much lift; the centrifugal failure mode