theophany
The term theophany is used to describe an appearance of God in the sensible realm. The classic example from the Hebrew scriptures/Old Testament is of the burning bush that appears to Moses in Exodus 3:2. The God of the Old Testament is famously unavailable for face-to-face encounters, though, saying in Exodus 33 "no man shall see me, and live."
Christian theologians argue that Christ actually appears in the Old Testament, and they refer to such instances as "Christophanies." Jewish theologians are not supportive of these interpretations.