The Collaborative International Dictionary of English v.0.48:

Interlope \In`ter*lope"\, v. i. [imp. & p. p. Interloped; p.
   pr. & vb. n. Interloping.] [See Interloper.]
   To run between parties and intercept without right the
   advantage that one should gain from the other; to traffic
   without a proper license; to intrude; to forestall others; to
   intermeddle.
   [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

25 Moby Thesaurus words for "interloping":
   encroachment, entrance, entrenchment, impingement, imposition,
   incursion, infiltration, influx, infringement, injection, inroad,
   insinuation, interference, interjection, interposition,
   interposure, interruption, intervention, intrusion, invasion,
   irruption, obtrusion, trespass, trespassing, unlawful entry