Try ideation.
Ideation is about generating many ideas without being hindered by creative, intellectual, or emotional constraints. You can ideate through brainstorming, mindmapping, co-creation, and more.
For more, see Interaction Design Foundation on ideation.
Also see our talk-back boards recipe.
This asynchronous research method allows users to write their answers to a question, which allows you to crowdsource the ideation process.