The Collaborative International Dictionary of English v.0.48:

Beggar \Beg"gar\, n. [OE. beggere, fr. beg.]
   1. One who begs; one who asks or entreats earnestly, or with
      humility; a petitioner.
      [1913 Webster]

   2. One who makes it his business to ask alms.
      [1913 Webster]

   3. One who is dependent upon others for support; -- a
      contemptuous or sarcastic use.
      [1913 Webster]

   4. One who assumes in argument what he does not prove. --Abp.
      Tillotson.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Beggar \Beg"gar\, v. t. [imp. & p. p. Beggared; p. pr. & vb.
   n. Beggaring.]
   1. To reduce to beggary; to impoverish; as, he had beggared
      himself. --Milton.
      [1913 Webster]

   2. To cause to seem very poor and inadequate.
      [1913 Webster]

            It beggared all description.          --Shak.
      [1913 Webster]

WordNet (r) 3.0 (2006):

beggar
    n 1: a pauper who lives by begging [syn: beggar, mendicant]
    v 1: be beyond the resources of; "This beggars description!"
    2: reduce to beggary [syn: beggar, pauperize, pauperise]

Moby Thesaurus II by Grady Ward, 1.0:

130 Moby Thesaurus words for "beggar":
   Arab, Bowery bum, almsman, almswoman, asker, baffle, bankrupt,
   beach bum, beachcomber, beggarly fellow, blighter, bloke, bo,
   budmash, bum, bummer, cadger, caitiff, casual, challenge, chap,
   charity case, coupon clippers, deadbeat, defy, derelict, devil,
   dogie, down-and-out, down-and-outer, drifter, drone, drunkard,
   fellow, freeloader, gamin, gamine, good-for-naught,
   good-for-nothing, guttersnipe, guy, hardcase, hobo, homeless waif,
   human wreck, idle rich, idler, impoverish, indigent, landloper,
   lazzarone, leisure class, loafer, losel, lounge lizard, lowlife,
   lumpen proletariat, man, mauvais sujet, mean wretch, mendicant,
   mendicant friar, mendicant order, moocher, mucker, mudlark,
   no-good, nonworker, panhandler, parasite, pauper, pauperize,
   pauvre diable, penniless man, person, petitioner, piker, pilgarlic,
   poor creature, poor devil, poor man, poorling, prayer, ragamuffin,
   ragman, ragpicker, reduce, rentiers, rounder, sad case, sad sack,
   schnorrer, scrounger, ski bum, skid-row bum, spiv, sponge, sponger,
   starveling, stiff, stray, street Arab, street urchin, suitor,
   sundowner, suppliant, supplicant, supplicator, surf bum, swagman,
   swagsman, tatterdemalion, tennis bum, the unemployable,
   the unemployed, tramp, truant, turnpiker, urchin, vag, vagabond,
   vagrant, vaurien, waif, waifs and strays, want, wastrel,
   welfare client, worthless fellow, wretch



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

BEGGAR. One who obtains his livelihood by asking alms. The laws of several
of the states punish begging as an offence.



The Devil's Dictionary (1881-1906):

BEGGAR, n.  One who has relied on the assistance of his friends.