The Collaborative International Dictionary of English v.0.48:

Fain \Fain\, a. [OE. fain, fagen, AS. f[ae]gen; akin to OS.
   fagan, Icel. faginn glad; AS. f[ae]gnian to rejoice, OS.
   fagan[=o]n, Icel. fagna, Goth. fagin[=o]n, cf. Goth.
   fah[=e]ds joy; and fr. the same root as E. fair. Srr Fair,
   a., and cf. Fawn to court favor.]
   1. Well-pleased; glad; apt; wont; fond; inclined.
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            Men and birds are fain of climbing high. --Shak.
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            To a busy man, temptation is fainto climb up
            together with his business.           --Jer. Taylor.
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   2. Satisfied; contented; also, constrained. --Shak.
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            The learned Castalio was fain to make trechers at
            Basle to keep himself from starving.  --Locke.
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The Collaborative International Dictionary of English v.0.48:

Fain \Fain\, adv.
   With joy; gladly; -- with wold.
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         He would fain have filled his belly with the husks that
         the swine did eat.                       --Luke xv. 16.
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         Fain Would I woo her, yet I dare not.    --Shak.
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The Collaborative International Dictionary of English v.0.48:

Fain \Fain\, v. t. & i.
   To be glad; to wish or desire. [Obs.]
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         Whoso fair thing does fain to see.       --Spencer.
   [1913 Webster] Faineance

WordNet (r) 3.0 (2006):

fain
    adv 1: in a willing manner; "this was gladly agreed to"; "I
           would fain do it" [syn: gladly, lief, fain]
    adj 1: having made preparations; "prepared to take risks" [syn:
           disposed(p), fain, inclined(p), prepared]

Moby Thesaurus II by Grady Ward, 1.0:

55 Moby Thesaurus words for "fain":
   aching for, acquiescent, agreeable, alacritous, amenable, ardent,
   bent on, compliant, consenting, content, cooperative, crazy to,
   desirous of, disposed, docile, dying for, dying to, eager,
   enthusiastic, fain of, favorable, favorably disposed,
   favorably inclined, fond of, forward, game, in the mind,
   in the mood, inclined, inclined toward, itching for, keen on,
   leaning toward, mad on, minded, partial to, pliant, predisposed,
   prompt, prone, quick, ready, ready and willing, receptive,
   responsive, set on, spoiling for, tractable, well-disposed,
   well-inclined, wild to, willed, willing, willinghearted, zealous