Merriam-Webster's Collegiate® Dictionary, 11th Edition
BLUR
I. noun
Etymology: perhaps akin to Middle English bleren to blear
Date: 1519
a smear or stain that obscures, something vaguely or indistinctly perceived,
II. verb (blurred; blurring)
Date: 1520
transitive verb to obscure or blemish by smearing, sully , to make dim, indistinct, or vague in outline or character, to make cloudy or confused, intransitive verb to make blurs, to become vague or indistinct, blurringly adverb