没頭【ぼっとう】
immersing oneself in, being absorbed in, devoting oneself to, giving oneself up entirely to
陥没【かんぼつ】
cave-in, collapse, sinking, depression (e.g. of the skull), subsidence
沈没【ちんぼつ】
sinking, foundering, going down, submersion, getting dead drunk, having too much fun (esp. in a red-light district, etc.) and missing work or neglecting one's duties, staying in one place for a long time
没収【ぼっしゅう】
forfeiture, seizure, confiscation, impounding
没落【ぼつらく】
ruin, fall, collapse, downfall, bankruptcy
埋没【まいぼつ】
being buried, remaining unknown, being forgotten, being absorbed (e.g. in research), being immersed
出没【しゅつぼつ】
making frequent appearances, appearing often, appearing and disappearing