An abnormal but benign thickening of the prickle-cell layer of the skin (as in psoriasis)

WordNet Word definitions in WordNet
n. an abnormal but benign thickening of the prickle-cell layer of the skin (as in psoriasis)

Wiktionary Word definitions in Wiktionary
n. (context medicine English) A benign abnormal thickening of the stratum spinosum, or prickle cell, layer of the epidermis.(First attested in the late 19th century.) (R:SOED5)

Wikipedia Word definitions in Wikipedia
Acanthosis is diffuse epidermal hyperplasia (thickening of the skin). It implies increased thickness of the Malpighian layer ( stratum basale and stratum spinosum ).