The Collaborative International Dictionary of English v.0.48:

Fortify \For"ti*fy\, v. t. [imp. & p. p. Fortified; p. pr. &
   vb. n. Fortifying.] [F. fortifier, L. fortificare; fortis
   strong + -ficare (in comp.) to make. See Fort, and -fy.]
   1. To add strength to; to strengthen; to confirm; to furnish
      with power to resist attack.
      [1913 Webster]

            Timidity was fortified by pride.      --Gibbon.
      [1913 Webster]

            Pride came to the aid of fancy, and both combined to
            fortify his resolution.               --Sir W.
                                                  Scott.
      [1913 Webster]

   2. To strengthen and secure by forts or batteries, or by
      surrounding with a wall or ditch or other military works;
      to render defensible against an attack by hostile forces.
      [1913 Webster]

WordNet (r) 3.0 (2006):

fortified
    adj 1: secured with bastions or fortifications [syn:
           bastioned, fortified]
    2: having something added to increase the strength; "fortified
       wine"