to test a new or undeveloped idea or proposal through multiple interactions, with the intent of further refining the underlying thinking to ensure readiness for the next stage, as in “We’ll need to do some rock tumbling of this investment thesis before we present it to our investors”; derives from the process of polishing rough gemstones in a spinning tumbler, resulting in smooth and glossy end products suitable for decorative use; see also baked and crisp, which refer to the final state rather than the process of achieving it