The Collaborative International Dictionary of English v.0.48:

Heifer \Heif"er\, n. [OE. hayfare, AS. he['a]hfore, he['a]fore;
   the second part of this word seems akin to AS. fearr bull,
   ox; akin to OHG. farro, G. farre, D. vaars, heifer, G.
   f[aum]rse, and perh. to Gr. ?, ?, calf, heifer.] (Zool.)
   A young cow.
   [1913 Webster]

WordNet (r) 3.0 (2006):

heifer
    n 1: young cow

Moby Thesaurus II by Grady Ward, 1.0:

114 Moby Thesaurus words for "heifer":
   Brahman, Indian buffalo, Partlet, aurochs, babe, baby, beef,
   beef cattle, beeves, biddy, bison, bitch, bossy, bovine,
   bovine animal, broad, brood mare, buffalo, bull, bullock, calf,
   carabao, cattle, chick, colleen, cow, critter, cutie, dairy cattle,
   dairy cow, dame, damoiselle, damsel, demoiselle, doe, dogie, doll,
   ewe, ewe lamb, filly, frail, gal, girl, girlie, guinea hen, gyp,
   hen, hind, hornless cow, hoyden, jenny, jeune fille, jill,
   junior miss, kine, lass, lassie, leppy, lioness, little missy,
   mademoiselle, maid, maiden, mare, maverick, milch cow, milcher,
   milk cow, milker, miss, missy, muley cow, muley head, musk-ox,
   nanny, nanny goat, neat, nymphet, ox, oxen, peahen, piece, roe,
   romp, schoolgirl, schoolmaid, schoolmiss, she-bear, she-goat,
   she-lion, skirt, slip, slut, sow, steer, stirk, stot, subdeb,
   subdebutante, subteen, subteener, teenybopper, tigress, tomato,
   tomboy, virgin, vixen, wench, wisent, yak, yearling,
   young creature, young thing, zebu



Easton's 1897 Bible Dictionary:

Heifer
   Heb. 'eglah, (Deut. 21:4, 6; Jer. 46:20). Untrained to the yoke
   (Hos. 10:11); giving milk (Isa. 7:21); ploughing (Judg. 14:18);
   treading out grain (Jer. 50:11); unsubdued to the yoke an emblem
   of Judah (Isa. 15:5; Jer. 48:34).

     Heb. parah (Gen. 41:2; Num. 19:2). Bearing the yoke (Hos.
   4:16); "heifers of Bashan" (Amos 4:1), metaphorical for the
   voluptuous females of Samaria. The ordinance of sacrifice of the
   "red heifer" described in Num. 19:1-10; comp. Heb. 9:13.


Bouvier's Law Dictionary, Revised 6th Ed (1856):

HEIFER. A young cow, which has not had a calf. A beast of this kind two
years and a half old, was held to be improperly described in the indictment
as a cow. 2 East, P. C. 616; 1 Leach, 105.