The Collaborative International Dictionary of English v.0.48:

Impingement \Im*pinge"ment\, n.
   The act of impinging.
   [1913 Webster]

WordNet (r) 3.0 (2006):

impingement
    n 1: influencing strongly; "they resented the impingement of
         American values on European culture" [syn: impingement,
         encroachment, impact]
    2: a sharp collision produced by striking or dashing against
       something [syn: impingement, impaction]

Moby Thesaurus II by Grady Ward, 1.0:

75 Moby Thesaurus words for "impingement":
   appulse, attouchement, brunt, brush, bulldozing, bulling, bump,
   cannon, carambole, caress, carom, clash, collision, concussion,
   contact, contingence, crack-up, crash, crump, crunch, encounter,
   encroachment, entrance, entrenchment, glance, graze, hammering,
   impact, impingence, imposition, incursion, infiltration, influx,
   infringement, injection, inroad, insinuation, interference,
   interjection, interloping, interposition, interposure,
   interruption, intervention, intrusion, invasion, irruption, jar,
   jolt, kiss, mauling, meeting, nudge, obtrusion, onslaught,
   osculation, percussion, ramming, rub, shock, sideswipe,
   sledgehammering, smash, smash-up, smashing, taction, tangency,
   tentative contact, thrusting, touch, touching, trespass,
   trespassing, unlawful entry, whomp