Merriam-Webster's Collegiate® Dictionary, 11th Edition
SCOWL
I. verb
Etymology: Middle English skoulen, probably of Scandinavian origin; akin to Danish skule to scowl
Date: 14th century
intransitive verb to contract the brow in an expression of displeasure, to exhibit a threatening aspect, transitive verb to express with a scowl, scowler noun scowlingly adverb
II. noun
Date: circa 1520
a facial expression of displeasure ; frown