Add this to your browser's search engine list and make it default:
{google:baseURL}search?q=%s+-site:pinterest.*
If on Firefox, do you need to add the optional search bar (with the magnifying glass) in order to access "Change Search Settings"? Because I'm not finding it anywhere.
Doesn't help with reverse image searches, which accounts for probably 90% of the times I end up clicking on a pinterest link.
That's a brilliant solution, thanks!
As much as I avoid giving google any of my money I would literally pay them to be able to block domains from results.