The term "thick mat" refers to a dense and cushioned surface that is often used for exercise or comfort. It suggests something that is thick, soft, and provides support. Full definition
Large populations formed thick mats that covered the body of the lake. (scientificamerican.com)
A long - haired dog with thick mats needs a different brush to a short - haired breed, so the «best» brush depends on your requirements. (thedogclinic.com)
Photos are printed on premium archival paper and come with an ultra thick mat. (styleathome.com)