The Collaborative International Dictionary of English v.0.48:

Obtrusive \Ob*tru"sive\, a.
   Disposed to obtrude; inclined to intrude or thrust one's self
   or one's opinions upon others, or to enter uninvited;
   forward; pushing; intrusive. -- Ob*tru"sive*ly, adv. --
   Ob*tru"sive*ness, n.
   [1913 Webster]

         Not obvious, not obtrusive, but retired. --Milton.
   [1913 Webster]

WordNet (r) 3.0 (2006):

obtrusive
    adj 1: undesirably noticeable; "the obtrusive behavior of a
           spoiled child"; "equally obtrusive was the graffiti"
           [syn: obtrusive, noticeable] [ant: unnoticeable,
           unobtrusive]
    2: sticking out; protruding

Moby Thesaurus II by Grady Ward, 1.0:

90 Moby Thesaurus words for "obtrusive":
   aggressively self-confident, arrant, arrogant, audacious, biggety,
   blatant, bold, brazen, brazenfaced, bumptious, busy, chesty, cocky,
   cold, colorful, conceited, conspicuous, contumelious, cool, crude,
   disdainful, extravagant, familiar, flagrant, flaring, flaunting,
   forceful, forward, garish, gaudy, glaring, gorgeous, hanging out,
   hubristic, immodest, importunate, in relief, in the foreground,
   insolent, insulting, interfering, interruptive, intervenient,
   intrusive, invasive, know-it-all, loud, lurid, meddlesome,
   meddling, meretricious, notable, noticeable, notorious, officious,
   ostensible, outstanding, overpresumptuous, overweening, overwise,
   peacockish, peacocky, perk, perky, pert, presuming, presumptuous,
   procacious, prominent, pronounced, puffed up, pushy, salient,
   screaming, self-conceited, self-opinionated, sensational,
   shameless, smart-alecky, spectacular, staring, stark-staring,
   sticking out, striking, stuck-up, swelled-headed, tawdry, uppish,
   uppity, vulgar