Also found in: Dictionary.
start on someone or something
1. to begin dealing with someone or something. We have finished talking about Gary, and now we will start on Bob. We will start on dessert after you have finished your broccoli.
2. to begin to castigate someone or something Don't start on me! I didn't do anything wrong! The politician started on the opposing party, and everyone in the audience cheered.
1. To begin doing some project: After dinner, I started on my homework.
2. To cause someone to begin some diet, medication, or other corrective action taken or undertaken routinely: The doctor started me on antibiotics.