رين 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.

• رَانَ Form 1

  1 رَانَ ذ , [aor. يَرِينُ,] inf. n. رَيْنٌ, [in its primary acceptation, app. signifies It was, or became, rusty, or covered with rust. And hence,] It (a garment, or piece of cloth,) was, or became, dirty, or filthy; syn…

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• رَيْنٌ

  رَيْنٌ ذ , originally an inf. n.: (Msb:) Rust that overspreads the sword and the mirror; (M;) rust that overspreads a polished thing: (Er-Rághib, TA:) or much dirtiness from rust: or simply dirt, filth, soil, or pollutio…

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