Merriam-Webster's Collegiate® Dictionary, 11th Edition
RASH
I. adverb
Etymology: Middle English (northern dialect) rasch quickly; akin to Old High German rasc fast
Date: 15th century
in a rash manner,
II. adjective
Date: 1509
marked by or proceeding from undue haste or lack of deliberation or caution , quickly effective, see: adventurous rashly adverb rashness noun
III. noun
Etymology: obsolete French rache scurf, from Old French raiche, from Vulgar Latin *rasica, from *rasicare to scratch, from Latin rasus, past participle of radere
Date: 1709
an eruption on the body, a large number of instances in a short period