What is the presbyterian definition of sacrament?

Presbyterians talk about sacraments as an "outward sign of an inward grace." In other Words, a sacrament is both a visible sign (the bread and wine in communion; water in baptism) and an inward reality of the grace of God.

Presbyterians only recognize two sacraments, baptism and communion, because they were the only practices commanded directly by Jesus in the New Testament.