Definition: Antiagglutinin is a protein that's essential in immune system but can be mutated by viruses or infections, affecting cell-to-cell interactions leading to antibodies. Detailed definition includes: 1. Antiagglutinin (Antibody-like) - A protein found within cells of the immune system. 2. Protein: Antibody-like - This refers to the structure and function of a particular protein. It has binding properties that bind to specific antigens, allowing an antibody to recognize and neutralize them. So in essence, it's a protein with antibodies like properties.