digress
     v 1: lose clarity or turn aside especially from the main subject
          of attention or course of argument in writing, thinking,
          or speaking; "She always digresses when telling a
          story"; "her mind wanders"; "Don't digress when you give
          a lecture" [syn: {stray}, {divagate}, {wander}]
     2: wander from a direct or straight course [syn: {sidetrack}, {depart},
         {straggle}]
Source: WordNet® 2.0