What is the dilation rate in dilated convolution as mentioned in the paper here.
I doubt it can be described any better than in the paper you are referencing, but to sum it up, the dilation factor tells how large are the gaps between elements in a feature map on which we apply a convolution filter:
If dilation = 1, we take every 1st element (no gaps). If dilation = 2, we take every 2nd (gaps of size 1). And so on.
The benefit of this approach is that the receptive field of units in the network can grow exponentially with the number of layers/parameters as compared to non-dilated convolutions.