It's really a flexible term. There have been various pronouncements though the years, but they tend to be couched in terms of "factors" to consider rather than black and white litmus tests.

From an FAA Chief Counsel opinion, 1979 – "A criminal conviction is not, in and of itself, grounds for denying a certificate on the basis of moral character. In determining whether a certificate may be issued, all relevant factors are considered. These include the nature of the felony for which the applicant was convicted, the number and frequency of the incidents involved, and the relationship of the incident or incidents to his responsibilities as a certificate holder. A conviction alone does not demonstrate a lack of capacity to display the required degree of care, judgement, and responsibility."

If you really want to do a survey of cases where the question came up, just go here: NTSB Opinions and Orders

Leave everything the way it is except put the words good moral character in the Words & Phrases box