Acromantula venom is the highly-prized secretion of the acromantula.
Almost impossible to collect from a living Acromantula, the venom dries out not long after an Acromantula's death, so the venom may fetch as much as 100 Galleons a pint.
Slughorn attends Aragog's funeral in order to harvest the venom from the body (HBP22).
Unknown but valuable uses.
Combines the Greek ακρος (acros/acro), meaning "high" and -mantula, from the Latin "tarantula" for "wolf spider."
From the Web
"Acromantula Venom" on the Harry Potter Wiki