Describe "aggressively"

So I'm coming home from "the city" on a major east/west highway in pouring rain that's beginning to look like freezing rain. The lights are all green as I'm going through town - as long as I stay in the left lane. As soon as we are past the area where semi-trucks have to stay in the right lane I have a large red semi pull out into the left lane behind me and starts tailgating me. He continues to crowd me all the way out of town (until I turned off the highway to go home) - even flashing his high beams at me trying to get me to move over to the right lane. My thoughts were that it was raining too hard and there was too much traffic to my right for me to get over - especially as my turn-off was on the left - and I was doing the speed limit as it was. As I turned left and he sped off I was able to get his liscense plate and words off the side of the cab to call in. I get ahold of the sheriff's office and the dispatcher says "describe aggressively" after she hears part of my tale. She also asked how fast I was going - 60 mph. Once she heard that she thanked me for calling it in. So I won't ever know if the truck got pulled over or not but I figure I did my part to attempt to avert an accident. In the meantime I'm amused at the dispatcher's questions and very very thankful I was able to make it safely home.