IPA: /rɪˈliːsər/
KK: /rɪˈliːsər/
A person who gives up a claim or right, especially in legal contexts.
The releasor signed the document to officially give up their claim to the property.
Releasor → It is formed from "release" (from Old French *relacier*, meaning to unfasten or let go) and "-or" (meaning a person who). A releasor is a person who lets go or unfastens something, typically in a legal context.
Think of someone who is 'letting go' ('release') of something, and the '-or' indicates that this person is the one performing the action.