May be a long-standing minor nonconformance from previous assessments, or a collection of similar minor nonconformances indicating a widespread problem;
Established as detrimental to quality delivered to customers; or
A failure or significant deficiency in a significant part of the quality system governed by applicable standards.
From LRQA:
LRQA calls a 'major' finding a HOLD POINT. They discourage talk about 'major' and 'minor' nonconformances.
ISO 19011 - Quality and Environmental Management Systems Auditing Forum Discussions