Thayer's Greek Lexicon

 1. the movable stick or trigger of a trap, a trap stick
  1) a trap, snare
  2) any impediment placed in the way and causing one to stumble or
fall, (a stumbling block, occasion of stumbling) i.e. a rock
which is a cause of stumbling
  3) fig. applied to Jesus Christ, whose person and career were so
contrary to the expectations of the Jews concerning the Messiah,
that they rejected him and by their obstinacy made shipwreck of
their salvation
2. any person or thing by which one is (entrapped) drawn into error or sin