This is the standard definition of consensus used since the 1960s and 1970s, and probably before. It was published in 1981 in United Judgement: The Handbook of Consensus Decision Making by the Center for Conflict Resolution.

The goal of consensus is a decision that is consented to by all members. Of course, full consent does not mean that everyone must be completely satisfied with the final outcome—in fact, total satisfaction is rare. The decision must be acceptable enough, however, that all will agree to support the group in choosing it.

This handbook was printed in typescript and circulated in various forms years before publication and is considered one of the classics. It was reprinted in 1999 by the Fellowship for Intentional Community and is available from their bookstore. They also have other books and reprints from Communities Magazine on consensus decision-making.