Standard metrics such as "revenue" and "orders" contain a convenient [?] icon in reports that displays the metric definition as shown in the example below...
...it would be great if we could add our own metric definitions to calculated metrics and custom events like events 33, 34, and 39 shown above.
Good idea, much more handy than notes in the report. As long as you could upload and share across report suites all your definitions rather than doing them individually.
In the absence of this, we make a glossary available to our users - sharing a matrix that covers all prop, event and evar definitions against their identifying numbers (which we've made consistent across all deployments).