مركل doesn't appear in Hans Wehr's Modern Standard Arabic dictionary, but Lane's Arabic-English Lexicon has 2 entries for it, distinguished by diacritics. Select one below for the full classical Arabic definition.

• مَرْكَلٌ

  مَرْكَلٌ ذ The part, of a beast, where one strikes him with the foot, or leg, (K, TA,) when putting him in motion for the purpose of [his] running: (TA:) the two such parts are termed the مَرْكَلَانِ: and the pl. is مَرَ…

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• مِرْكَلٌ

  مِرْكَلٌ ذ The foot, or leg, [as being the instrument with which the action termed رَكْلٌ is performed:] in the copies of the K, الرَّجُلُ is erroneously put for الرِّجْلُ: or, accord. to the L, the foot, or leg, of the …

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