polycondensation
noun
poly·con·den·sa·tion ˌpä-lē-ˌkän-ˌden-ˈsā-shən 
-dən-
: a chemical condensation leading to the formation of a compound of high molecular weight
Word History
Etymology
borrowed from German Polykondensation, from poly- poly- + Kondensation condensation
First Known Use
1936, in the meaning defined above