Best way is can explain is that my tummy suddenly gets really tight and hard. It literally feels like a big hard bowling ball. Its not painful, just uncomfortable, and releases soon after. I've been having them since 18wks this time and I coukd actually see them on the screen at my morphology scan which was pretty weird!
Nailed it :) for me it felt like a tightness and a release it doesn't always hurt for all women.
like your tummy gets tight and hard then releases and goes back to normal it's basically your body preparing itself for the actual thing.
Best of luck