noun.
The protein constituent of hemoglobin and myoglobin.
The Century Dictionary and Cyclopedia
noun.
The proteid substance which with hematin makes up the larger part of the red blood-corpuscles. It is possibly a mixture of several distinct proteids.
the GNU version of the Collaborative International Dictionary of English
noun.
a colorless protein obtained by removing heme from hemoglobin; the protein part of hemoglobin.