1. To act more cautiously than one did before. I just got this quarter's budget report, and we definitely need to haul in our horns and spend less going forward.

2. To withdraw from or back off a particular stance or opinion. Once I found out that Uncle Ned was opposed to that measure, I hauled in my horns on praising it.

3. To act or spend more frugally. I really need to haul in my horns because I don't get paid for another two weeks.