A cast iron type with eutectic composition, i.e. with a degree of saturation of 1.0 or a carbon equivalent of 4.3 % is referred to as eutectic cast iron.
Additional references:
Eutectic
Eutectic graphite quantity
Eutectic grain
Eutectic grain count
Eutectic alloy
Eutectic temperature
Metal matrix of cast iron
Structure formation of cast iron