random coil

in polymers
Synonym: statistical coil
The complete set of spatial arrangements of a chain molecule with a large number of segments that randomly change mutual orientation with time, under conditions in which it is free from external constraints that would affect its conformation. If the solution of the chain molecules is not in a theta state, the segments change mutual orientation only approximately randomly. Synonymous with statistical coil.
Purple Book, 1st ed., p. 50 (http://old.iupac.org/publications/books/author/metanomski.html)