1) Like some facial tissue 2) Multilayer thickness 3) Tissue descriptor 
• (a.) Consisting of three distinct webs inwrought together in weaving, as cloth or carpeting; having three strands; threefold.
Three'-ply` adjective Consisting of three distinct webs inwrought together in weaving, as cloth or carpeting; having three strands; threefold. 
[adj] - having a thickness made up of three layers or strands
adjective having a thickness made up of three layers or strands; `three-ply cloth`; `three-ply yarn`