The Collaborative International Dictionary of English v.0.48:

Abb \Abb\ ([a^]b), n. [AS. [=a]web, [=a]b; pref. a- + web. See
   Web.]
   Among weavers, yarn for the warp. Hence, abb wool is wool
   for the abb.
   [1913 Webster]

WordNet (r) 3.0 (2006):

ABB
    n 1: an urban hit squad and guerrilla group of the Communist
         Party in the Philippines; formed in the 1980s [syn: Alex
         Boncayao Brigade, ABB, Revolutionary Proletarian Army,
         RPA-ABB]