WordNet (r) 3.0 (2006):

loan shark
    n 1: someone who lends money at excessive rates of interest
         [syn: usurer, loan shark, moneylender, shylock]

Moby Thesaurus II by Grady Ward, 1.0:

21 Moby Thesaurus words for "loan shark":
   Shylock, accommodate with, advance, banker, float a loan,
   lease-lend, lend, lend-lease, lender, loan, loan officer, loaner,
   money broker, moneylender, moneymonger, mortgage holder, mortgagee,
   negotiate a loan, pawnbroker, shark, usurer