Schaff's Bible Dictionary
OFFEND', OFFENSE'. V. (as Matt 5:29; Matt 18:6. " And so the noun means "that which causeth to stumble," or leads to sin. It is in these senses that the eye is said "to offend" (better "causeth thee to stumble"), Matt 5:29 - that is, it may allure to sin. So, in Matt 18:7, "offenses" are causes of sin. Our Saviour is said to be a "rock of offense," Rom 9:33, because the humility of his life and death was an obstacle in the way of the Jews' accepting him, as they associated with their idea of the Messiah the external grandeur and pomp of the world.
The "offense of the cross," Gal 5:11, is that in the doctrines of Christ or in the cross which is offensive to the natural man.