This entry refers to a theological term, and not to the so-called “Sound Doctrine church” which is an unhealthy church at best.
Agreeing with and faithful to biblical teaching and to orthodoxy beyond a bare minimum, such that Christians may be encouraged to continue in this way. Contrasted with aberrational, which refers to orthodox teaching or practice which is only barely so. Its opposite, “unsound” may be used to express degrees of deficiency in soundness.
– Source: A Biblical Guide To Orthodoxy And Heresy, Christian Research Journal, Summer 1990, by Robert M. Bowman.
See also: Essential doctrines of the Christian faith