It's another term for a spiral, especially when talking about spiraled strands of DNA
Definition b includes two kinds of 3-dimensional relatives of spirals: 
... Quite explicitly, b also includes a cylindrical coil spring and a strand of DNA, ... 
around a fixed axis, the shape of the curve remains fixed but its size grows in a... [DOC] [TLE] Nucleotides and the double helix - Life Sciences Cyberbridge [PAR] In this unit, the molecular structure of DNA and its packaging within cells will be ... 
helix because there are two intertwined strands within each molecule of DNA.