The Collaborative International Dictionary of English v.0.48:

Jar \Jar\, v. i. [imp. & p. p. Jarred; p. pr. & vb. n.
   Jarring.] [Cf. OE. charken to creak, AS. cearcian to gnash,
   F. jars a gander, L. garrire to chatter, prate, OHG. kerran
   to chatter, croak, G. quarren to grumble, and E. jargon,
   ajar.]
   [1913 Webster]
   1. To give forth a rudely quivering or tremulous sound; to
      sound harshly or discordantly; as, the notes jarred on my
      ears.
      [1913 Webster]

            When such strings jar, what hope of harmony ?
                                                  --Shak.
      [1913 Webster]

            A string may jar in the best master's hand.
                                                  --Roscommon.
      [1913 Webster]

   2. To act in opposition or disagreement; to clash; to
      interfere; to quarrel; to dispute.
      [1913 Webster]

            When those renowned noble peers Greece
            Through stubborn pride among themselves did jar.
                                                  --Spenser.
      [1913 Webster]

            For orders and degrees
            Jar not with liberty, but well consist. --Milton.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Jarring \Jar"ring\, a. [See Jar.]
   Shaking; disturbing; discordant. "A jarring sound." --Dryden.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Jarring \Jar"ring\ n.
   1. A shaking; a tremulous motion; as, the jarring of a
      steamship, caused by its engines.
      [1913 Webster]

   2. Discord; a clashing of interests. "Endless jarrings and
      immortal hate." --Dryden.
      [1913 Webster]

WordNet (r) 3.0 (2006):

jarring
    adj 1: making or causing a harsh and irritating sound; "the
           jarring noise of the iron gate scraping on the sidewalk"

Moby Thesaurus II by Grady Ward, 1.0:

123 Moby Thesaurus words for "jarring":
   agitating, ajar, antagonistic, antipathetic, astonishing,
   at cross-purposes, at loggerheads, at odds, at variance, at war,
   bouncy, breathtaking, bumpy, charged, choppy, clashing,
   cliff-hanging, conflicting, confused, contradictory, contrary,
   cranky, cross, differing, disaccordant, disagreeable, disagreeing,
   discordant, discrepant, disharmonious, disproportionate,
   disquieting, dissident, dissonant, distracting, disturbing,
   divergent, dry, electric, electrifying, exciting, exhilarating,
   galvanic, grating, grinding, harsh, heady, heart-expanding,
   heart-stirring, heart-swelling, heart-thrilling, hoarse, hostile,
   immiscible, impressive, inaccordant, incompatible, inflammatory,
   inharmonious, intoxicating, jangling, jangly, jogglety, joggling,
   joggly, jolting, jolty, jostling, maddening, mind-blowing, moving,
   negative, nerve-jangling, nerve-racking, nerve-rending,
   nerve-shaking, nerve-trying, out of accord, out of whack,
   overcoming, overmastering, overpowering, overwhelming, perturbing,
   piquant, provocative, provoking, rasping, raspy, raucous,
   ravishing, repugnant, rough, scraping, scrapy, scratching,
   scratchy, shocking, soul-stirring, spirit-stirring, staggering,
   startling, stimulating, stimulative, stirring, strident,
   stridulous, striking, stunning, surprising, suspenseful,
   suspensive, tantalizing, telling, thrilling, thrilly, troubling,
   uncongenial, unharmonious, unsettling, upsetting, variant,
   warring