big·a·my 
(bĭgə-mē)
(bĭgə-mē)n.
The criminal offense of marrying one person while still legally married to another.
[Middle English bigamie, from Old French, from Medieval Latin bigamia, from Late Latin bigamus, twice married : Latin bi-, two; see BI-1 + Greek gamos, marriage; see -GAMOUS.]
biga·mist n.