Meaning 1 ►▼
to ride a horse with rough shoes on its hooves over something
The cowboys rode roughshod over the trail in order to get the cattle to market on time.
Meaning 2 ►▼
to treat someone poorly
Please don't ride roughshod on the new employee. Be nice.
When cowboys took cattle a long distance to market the shoes on their horses became rough and would tear up the trail.