Qenya
tundo
noun. hill, mound, hill, mound [isolated]
tundo
noun. hole
ambo
noun. hill
There are more words but they are from Tolkien's earlier conceptional periods. Tolkien likely changed these words as he evolved the aesthetics and completeness of the languages. You may even find languages that Tolkien later rejected. Do not mix words from different time periods unless you are familiar with the phonetic developments.
Below: Tolkien's Late Period (1950–1973). These are from Tolkien's late conceptual period — his most settled forms of the languages. Prefer these over the earlier ones above when composing new text.
A noun in The Etymologies of the 1930s glossed “hill, mound” derived from the root ᴹ√TUN (Ety/TUN). Tolkien’s continued use of Q. Túna for the name of a hill in Valinor implies the ongoing validity of its root, so perhaps this word remained valid as well.
Neo-Quenya: For purposes of Neo-Quenya, I would assume that tundo refers mainly to a single isolated hill standing out from its surroundings, as opposed to Q. ambo for hills in general, but that’s speculation on my part.
Conceptual Development: In the Declension of Nouns from the early 1930s, ᴹQ. tundo (tundu-) meant “hole” instead (PE21/8). In Early Noldorin documents of the 1920s, ᴱQ. tunda was given as the cognate of ᴱN. tonn “hole” (PE13/122, 165).