The Collaborative International Dictionary of English v.0.48:

groan \groan\ (gr[=o]n), v. i. [imp. & p. p. Groaned
   (gr[=o]nd); p. pr. & vb. n. Groaning.] [OE. gronen, granen,
   granien, AS. gr[=a]nian, fr. the root of grennian to grin.
   [root]35. See 2d Grin, and cf. Grunt.]
   1. To give forth a low, moaning sound in breathing; to utter
      a groan, as in pain, in sorrow, or in derision; to moan.
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            For we . . . do groan, being burdened. --2 Cor. v.
                                                  4.
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            He heard the groaning of the oak.     --Sir W.
                                                  Scott.
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   2. To strive after earnestly, as with groans.
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            Nothing but holy, pure, and clear,
            Or that which groaneth to be so.      --Herbert.
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