مزلة 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.

• مَزَلَّةٌ

  مَزَلَّةٌ ذ : see the next paragraph. [Its primary signification is probably A cause of slipping: compare مَبْخَلَةٌ and مَجْبَنَةٌ &c.]…

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• مَزِلَّةٌ

  مَزِلَّةٌ ذ and , (S, Msb, K,) the former the more chaste, (Msb,) the latter mentioned by AA, (TA,) A slippery place; (S, Msb, K, TA;) such as a smooth rock, and the like; and such the صِرَاط is said to be. (TA.) [See al…

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