leech off someone Definition

leech¹
noun leeches

1. Any of various annelid worms with a cylindrical or flattened body bearing suckers at each end, especially a blood-sucking species which was formerly used for bloodletting as a treatment for many ailments.
2. A person who befriends another in the hope of personal gain.

Thesaurus: freeloader, parasite, sycophant.
3. archaic
A doctor or physician.

verb

leeches, leeched, leeching
1. medicine., archaic
To treat (a patient) by applying leeches.

Etymology: Anglo-Saxon læce.

Phrasal Verb: leech off someone or something

To use them or it to one's advantage, usually without permission and often in an objectionable way.

Phrasal Verb: leech on to someone or something

To cling to them or it.