Affusion

Affusion is a method of baptism where water is poured on the head of the person being baptized.

This may be due to the practical difficulties and dangers of drowning and hypothermia associated with totally immersing an infant in cold water.

But if you have neither, pour out water three times upon the head into the name of Father and Son and Holy Spirit.

Acts of various martyrs show that many were baptized in prison, while awaiting martyrdom; immersion would have been impossible.

Receiving this baptism was regarded as a bar to Holy Orders, but this sprang from the person's having put off baptism until the last moment—a practice that in the fourth century became common, with people enrolling as catechumens but not being baptized for years or decades.

Also noteworthy to affusionists is that, in Luke 11:38, the word ἐβαπτίσθη [ebaptisthē][8] is used in the Greek and baptizatus[9] is used in the Latin.