The Collaborative International Dictionary of English v.0.48:

Shekel \Shek"el\, n. [Heb. shegel, fr. sh[=a]gal to weigh.]
   1. An ancient weight and coin used by the Jews and by other
      nations of the same stock.
      [1913 Webster]

   Note: A common estimate makes the shekel equal in weight to
         about 130 grains for gold, 224 grains for silver, and
         450 grains for copper, and the approximate values of
         the coins are (gold) $5.00, (silver) 60 cents, and
         (copper half shekel), one and one half cents.
         [1913 Webster]

   2. pl. A jocose term for money.
      [1913 Webster]

WordNet (r) 3.0 (2006):

shekel
    n 1: the basic unit of money in Israel

Easton's 1897 Bible Dictionary:

Shekel
   weight, the common standard both of weight and value among the
   Hebrews. It is estimated at 220 English grains, or a little more
   than half an ounce avoirdupois. The "shekel of the sanctuary"
   (Ex. 30:13; Num. 3:47) was equal to twenty gerahs (Ezek. 45:12).
   There were shekels of gold (1 Chr. 21:25), of silver (1 Sam.
   9:8), of brass (17:5), and of iron (7). When it became a coined
   piece of money, the shekel of gold was equivalent to about 2
   pound of our money. Six gold shekels, according to the later
   Jewish system, were equal in value to fifty silver ones.

     The temple contribution, with which the public sacrifices were
   bought (Ex. 30:13; 2 Chr. 24:6), consisted of one common shekel,
   or a sanctuary half-shekel, equal to two Attic drachmas. The
   coin, a stater (q.v.), which Peter found in the fish's mouth
   paid this contribution for both him and Christ (Matt. 17:24,
   27). A zuza, or quarter of a shekel, was given by Saul to Samuel
   (1 Sam. 9:8).