The Collaborative International Dictionary of English v.0.48:

Inroad \In"road`\ ([i^]n"r[=o]d`), n.
   The entrance of an enemy into a country with purposes of
   hostility; a sudden or desultory incursion or invasion; raid;
   encroachment.
   [1913 Webster]

         The loss of Shrewsbury exposed all North Wales to the
         daily inroads of the enemy.              --Clarendon.
   [1913 Webster]

         With perpetual inroads to alarm,
         Though inaccessible, his fatal throne.   --Milton.

   Syn: Invasion; incursion; irruption. See Invasion.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Inroad \In*road"\ ([i^]n*r[=o]d"), v. t. [imp. & p. p.
   Inroaded; p. pr. & vb. n. Inroading.]
   To make an inroad into; to invade. [Obs.]
   [1913 Webster]

         The Saracens . . . conquered Spain, inroaded Aquitaine.
                                                  --Fuller.
   [1913 Webster]

WordNet (r) 3.0 (2006):

inroad
    n 1: an encroachment or intrusion; "they made inroads in the
         United States market"
    2: an invasion or hostile attack