swear at something—curse smth.:
- The accident was holding up traffic heading for a major football event, and he could hear people swearing at the delay.
swear on something—
1. (also: swear by something ) call smth. held holy as witness to the truth of what one says:
- I swear on my soul that this really happened.
2. (also: swear to something) have great confidence in the value of smth. (often negat.):
- I can’t swear on the quality for all of his models, but this one was really decent for the price.