A noun for “collapse, downfall” mentioned in notes for the Markirya poem of the 1950s along with its adjectival form atalantëa (MC/223), likely derived from the root √TALAT. It is also used as one of the names of Númenor: Atalantë “Downfall(en)” (S/281; Let/347).

It seems Tolkien originally based this noun on the past tense of the verb [ᴹQ.] atalta- “collapse, fall in” (Ety/TALÁT); the past form atalante “down-fell” appears in various versions of the ᴹQ. Lament of Atalante from the 1930s and 40s (LR/47, 56; SD/247, 249, 310). This form was also mentioned as an (archaic?) “perfective” past tense atalante “slipped down, fell in ruin” [vs. ordinary past talante “slipped, slid”] of the talat-stem verb talta- in the second version of Tengwesta Qenderinwa from around 1950 (TQ2), though the notes where it appeared were rejected (PE18/88 note #83).