ADJ.
bilabial
LABIODENTAL + NOUN
consonants, fricatives, spirant
adj
articulated with the lower lip and upper teeth.
/f/ and /v/ are labiodental consonants.
noun
A speech sound articulated with the lower lip and upper teeth.
In English, F and V are labiodental fricatives.
Ef was probably a bilabial, not a labiodental spirant, as is also evident from Goth.