1.
a. To give rise to; cause to occur: set off a chemical reaction.
b. To cause to explode: set off a bomb.
c. To make suddenly or demonstrably angry: The clerk's indifference finally set me off.
2. To indicate as being different; distinguish: features setting him off from the crowd.
3. To direct attention to by contrast; accentuate: set off a passage with italics.
4. To counterbalance, counteract, or compensate for: Our dismay at her leaving was set off by our knowing that she was happy.
5. To start on a journey: set off for Europe.