To be very unwieldy or unmanageable; to be nearly impossible to organize. Usually said of a group of people. Getting all of the extended family into their right places for the reunion photo was like herding cats! It's like herding cats trying to manage all these different software development teams.

To attempt to coordinate or control subjects that are uncooperative. Often used as a point of comparison in the phrase "like herding cats." Trying to get my two toddlers out the door these days is like herding cats!