v.tr.1. To make sweet or sweeter by adding sugar, honey, saccharin, or another sweet substance.
2. To make more pleasant or agreeable.
3. To soften or soothe: sweetened her mood.
4. To make bearable; alleviate.
5. Informal a. To increase the value of (collateral for a loan) by adding more securities.
b. To enhance the attractiveness or financial desirability of (an offer, for example).
6. Games To increase the value of (an unwon poker pot) by adding stakes before reopening.
7. To make less acidic: sweeten the stomach with antacids.
8. To remove sulfur compounds from (fuel oil or gas).