Noah Webster's New International Dictionary of the English Language

1. (a.) Having the right or just claim; as, the rightful owner; being or holding by right; as, the rightful heir to a throne or an estate; a rightful king.

2. (a.) Righteous; upright; just; good; -- said of persons.

3. (a.) Consonant to justice; just; as, a rightful cause.

4. (a.) Belonging, held, or possessed by right, or by just claim; as, a rightful inheritance; rightful authority.