Sindarin 

rond

noun. (vaulted or arched) roof, heavens [as roof of the world], vault, high roofed cavern, vaulted chamber or cavern, vaulted or arched roof as seen from below (and usually not visible from outside); a (large) hall or chamber so roofed, vaulted or arched roof, large hall or chamber so roofed; heavens
Sindarin [RC/421.2803; SA/os(t).013; SA/rond.001; WJ/414.2406; WJ/415.0707] Group: Eldamo. Published by

rond

noun. cave roof
Sindarin [Ety/384, VT/46:12, S/437, WJ/414, X/RH, X/ND1] Group: Hiswelókë's Sindarin Dictionary. Published by

rond

noun. vaulted or arched roof, as seen from below (and usually not visible from outside), or a (large) hall of chamber so roofed
Sindarin [Ety/384, VT/46:12, S/437, WJ/414, X/RH, X/ND1] Group: Hiswelókë's Sindarin Dictionary. Published by

gathrod

noun. cave
Sindarin Group: Eldamo. Published by

roth

noun. cave

n. cave. Q. rondo.

Sindarin [(PE17 Sindarin Corpus) PE17:117] -. Group: Parma Eldalamberon 17 Sindarin Corpus. Published by

groth

noun. cave, tunnel, large excavation
Sindarin [WJ/415, S/431, VT/46:12] Group: Hiswelókë's Sindarin Dictionary. Published by

groth

noun. delving, underground dwelling
Sindarin [WJ/415, S/431, VT/46:12] Group: Hiswelókë's Sindarin Dictionary. Published by

feleg

noun. cave

n. cave, mine, underground dwelling. Q. felco. Q.

Sindarin [(PE17 Sindarin Corpus) PE17:118] -. Group: Parma Eldalamberon 17 Sindarin Corpus. Published by

* rond

hall with vaulted roof

rond (construct ron) (cave, cavern, vault, vaulted ceiling), pl. rynd (idh rynd), coll. pl. ronnath

* rond

vault, vaulted ceiling

rond (construct ron) (cave, cavern, hall with vaulted roof), pl. rynd (idh rynd), coll. pl. ronnath

* grôd

cave

1) grôd (i **rôd, construct grod) (delving, excavation, underground dwelling), pl. grŷd (in grŷd) (WJ:414), 2) groth (i **roth) (delving, large excavation), pl. gryth (in gryth) (VT46:12), 3) rond (construct ron) (cavern, vault, vaulted ceiling, hall with vaulted roof), pl. rynd (idh rynd), coll. pl. ronnath, 4) roth (delving, large excavation), pl. ryth, 4) gathrod (i **athrod), pl. gethryd (i ngethryd = i ñethryd), 5) fela (pl. fili). In the Etymologies (LR:381 s.v. PHÉLEG) the name Felagund is said to include this word, but since Tolkien later re-explained this name as a borrowing from Dwarvish, some would consider fela** as a word for ”cave” conceptually obsolete.