am·y·loid 
(ămə-loid′)
(ămə-loid′)n.
1. A starchlike substance.
2.
a. An insoluble, fibrous structure consisting chiefly of an aggregation of proteins arranged in beta sheets, forming extracellular deposits in organs or tissues and characteristic of certain diseases such as Alzheimer's disease and Parkinson's disease.
b. The substance that makes up such a structure.
adj.
1. Starchlike.
2. Being or related to proteinaceous amyloid: amyloid plaque.