$ brew install pv
# diskutil list
# diskutil unmountDisk /dev/disk2
# sudo dd if=~/Downloads/ubuntu-16.04.3-server-amd64.iso | sudo pv -s 865M| sudo dd of=/dev/disk2
105MiB 0:00:54 [2.09MiB/s] [===> ] 12% ETA 0:06:28
and if anything goes wrong and the disk is corrupted, likely Disk Utility
won't be worth a damn. reformat with commandline
sudo diskutil eraseDisk HFS+ name /path/to/disk