Proposer
/prəˈpəʊzər/
Definition 1 of 1
Pro Tip 1/3Idea Originator
Refers to someone who first thinks of a suggestion or concept, often in a formal setting like a meeting. 
As the proposer of the project, Jane will outline the initial steps.
Pro Tip 2/3Active Role
Implies someone actively involved in the discussion or planning process, not a passive participant. 
Mike, the proposer of the motion, argued passionately for policy changes.
Pro Tip 3/3Not an Implementer
Being the proposer does not necessarily mean one is responsible for implementing the idea. 
As the proposer, Sara's job was done once the committee approved her proposal.