'four-ply' definitions:

Definition of 'four-ply'

From: WordNet
adjective
Having a thickness made up of four layers or strands; "four-ply yarns"

Definition of 'four-ply'

From: GCIDE
  • four-ply \four-ply\ adj. having a thickness made up of four layers or strands; as, four-ply yarns. [WordNet 1.5]