رهدن doesn't appear in Hans Wehr's Modern Standard Arabic dictionary, but Lane's Arabic-English Lexicon has 5 entries for it, distinguished by diacritics. Select one below for the full classical Arabic definition.

• رَهْدَنَ Form Q. 1

  Q. 1 رَهْدَنَ ذ , (TA,) inf. n. رَهْدَنَةٌ, (K, TA,) He circled in walking [like the bird called رَهْدَنٌ]: (K, TA:) or he was as though he circled in his gait. (Az, TA.) See رَهْدَنٌ. -b2- He was, or became, slow, tardy…

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• رَهْدَنٌ

  رَهْدَنٌ ذ (S, K) and and (K) A certain bird, in Mekkeh, like the عُصْفُور [or sparrow]; (S, K;) as also , and and : (K:) and a certain bird resembling the جُمَّر, [which is said by Es-Sakháwee, cited in the Msb in art. …

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• رُهْدَنٌ

  رُهْدَنٌ ذ : see the next preceding paragraph.…

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• رُهْدُنٌ

  رُهْدُنٌ ذ , without teshdeed, (assumed tropical:) A heavy [or slow] man. (JK.)…

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• رِهْدَنٌ

  رِهْدَنٌ ذ : see رَهْدَنٌ.…

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