noun
bigamy
Legal and social term for being married to two people at the same time.
二重結婚は法律で禁止されている。
Bigamy is prohibited by law.
重婚 is a broader legal term for plural marriage, while 二重結婚 specifically refers to bigamy (two spouses).
Compound of 二重 (double) and 結婚 (marriage), directly meaning 'double marriage'.