سير 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.

• سَارَ Form 1

  1 سَارَ ذ , aor. يَسِيرُ, inf. n. سَيْرٌ and مَسِيرٌ, (S, M, A, Mgh, Msb, K,) which latter is extr., for by rule it should be of the measure مَفْعَلٌ, with fet-h [to the ع], (S,) and مَسِيرَةٌ (M, K) and سَيْرُورَةٌ (M, …

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• سَيْرٌ

  سَيْرٌ ذ an inf. n. of 1 [q. v.]. (S, M, A, &c.) [Used as a simple subst., A going, in any manner, or any pace; passage, march, journey, progress, or course: a pace: pace as meaning degree of celerity, or rate of going: …

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