Denshi Jisho — Online Japanese dictionary

ほら cave; den; grotto
Common word, Noun 
うろ hollow; cavity; hole
Noun 
くうどう cave; hollow; cavity
Common word, Noun 
せつどう snow cave
Noun 
ふうどう wind tunnel
Noun 
ぼんぼり paper-covered lamp or lantern
Noun 
るいどう sinusoid (in anatomy)
Noun, No-adjective 
しょうどう druse (globular calcium oxalate crystals, often lining a rock cavity)
Noun 
石灰 せっかいどう limestone cave
Noun 
溶岩 ようがんどう lava tube
Noun 
海食 かいしょくどう sea cave; marine cave
Noun 
鍾乳 しょうにゅうどう limestone cave (cavern, grotto)
Common word, Noun 
鐘乳 しょうにゅうどう limestone cave (cavern, grotto)
Noun 
静脈 じょうみゃくどう venous sinus; sinus venosus
Noun 

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