Easton's Bible Dictionary

Occurs only in Proverbs 30:15 (Hebrews `alukah); the generic name for any blood-sucking annelid. There are various species in the marshes and pools of Palestine. That here referred to, the Hoemopis, is remarkable for the coarseness of its bite, and is therefore not used for medical purposes. They are spoken of in the East with feelings of aversion and horror, because of their propensity to fasten on the tongue and nostrils of horses when they come to drink out of the pools. The medicinal leech (Hirudo medicinalis), besides other species of leeches, are common in the waters of Syria.

Noah Webster's New International Dictionary of the English Language

1. (n.) A large blood-sucking leech (Haemopsis vorax), of Europe and Northern Africa. It attacks the lips and mouths of horses.

2. (n.) A farrier; a veterinary surgeon.