The Quenya verb for “to fall”, dating all the way back to the Qenya Lexicon of the 1910s, though in that document it had the form ᴱQ. lant- and the additional gloss “drop” (QL/51). In the Qenya Lexicon it was derived from the early root ᴱ√LANTAN [LṆTṆ], but in The Etymologies of the 1930s Tolkien changed the root {ᴹ√LANTA >>} ᴹ√DA(N)T “fall down” as the basis for ᴹQ. lanta- “to fall” (Ety/DAT; EtyAC/LANTA). Q. lanta- “fall” appeared regularly in Tolkien’s later writings as well (MC/222; PE17/62; VT49/47), most notably in the Namárië poem in its first phrase: ai! laurië lantar lassi súrinen “ah! like gold fall the leaves in the wind” (LotR/377).
The word lanta was occasionally used as a noun for “a fall”; see that entry for discussion.
Neo-Quenya: In Tolkien’s later writings, lanta- was used only for intransitive “fall”. However, we have no Quenya verbs for transitive “drop” other than 1910s ᴱQ. lant-, so I would assume that lanta- can be used this way as well for purposes of Neo-Quenya (QL/51). For example, lantan “I fall” vs. lantan i macil “I drop [make fall] the sword”.
lanta (1) noun "a fall" (DAT/DANT (TALÁT) ), also lantë.