ركم1 رَكَمَ الشَّىْءَ, aor. ـُ (S, M,) inf. n. رَكْمٌ (M, K,) He heaped up, piled up, or accumulated, the thing; i. e. he collected together the thing, and put, or threw, one part of it upon another; (S, K; *) or he put, or threw, one part of the thing upon another. (M, TA.) 6 تراكم and ↓ ارتكم It (a thing) was, or became heaped, or piled, up, or together, or accumulated; i. e., collected together, (S, K, TA,) one part upon [or overlying] another. (TA.) You say, تراكم السَّحَابُ The clouds were, or became, [heaped, or piled, up,] one above, or upon, [or overlying,] another; as also تراكب. (TA in art. ركب.) And تراكم لَحْمُ النَّاقَةِ [lit. The flesh of the she-camel became accumulated]; meaning the she-camel became fat. (TA.) [And تراكمت الظَّلْمَةُ (assumed tropical:)  The darkness became condensed, or dense:  for the Arabs describe thick darkness as “ darknesses  one above another: ” see Kur xxiv. 40.] and تراكمت الأَشْغَالُ and ↓ ارتكمت (tropical:)  [Occupations, or the occupations, became accumulated]. (TA.) 8 إِرْتَكَمَ see the next preceding paragraph, in two places.رَكَمٌ: see رُكَامٌ.رُكْمَةٌ, (S, K, [so in my copies of the S,]) with  damm, (K,) in [some of] the copies of the S رَكَمَةٌ, (TA,) Clay, or mud, (S, K, TA,) and earth, or dust, (TA,) collected together [and app. heaped up]. (S, K, TA.) رُكَامٌ (S, K) and ↓ رَكَمٌ (IAar, K) and ↓ مُتَرَاكِمٌ (S, K) and ↓ مُرْتَكِمٌ and ↓ مَرْكُومٌ (TA) Clouds (سَحَابٌ) collected together, and heaped, or piled, up; (IAar, S, K, TA;) and so sand; (S, TA;) and the like: (S:) [or, as the explanations seem to indicate, the first and second are used as substs., implying what is collected together &c; and the rest only as epithets:] and you say also رُكَامُ سَحَابِ (TA) and رُكَامُ رَمْلٍ: (K, TA:) and شَىْءٌ رُكَامٌ means a thing accumulated, one part upon another. (TA.) b2:  And قَطِيعٌ رُكَامٌ (tropical:)  A large herd or flock or the like; (K, TA;) likened to the ركام of clouds or of sand. (TA.) مَرْكُومٌ: see the next preceding paragraph. b2: [Hence,] نَاقَةٌ مَرْكُومَةٌ (tropical:)  A fat she-camel. (TA. [See 6.]) b3:  مَرْكُومٌ is applied by Dhu-r-Rummeh as an epithet to midnight (جَوْزُ اللَّيْلِ) [meaning مَرْكُومٌ ظُلُمَاتُهُ, i. e. Densely dark, as though its darknesses were heaped one upon another: see 6]. (TA in art. خفق.) مُرْتَكَمٌ (tropical:)  The main part, or middle, of a road. (S, K, TA.) مُرْتَكِمٌ: see رُكَامٌ.مُتَرَاكِمٌ: see رُكَامٌ.