There's just one problem with the word "bigerminal" - it doesn't actually exist! However, if it did, its spelling would follow the phonetic transcription /baɪˈdʒɜː.mɪ.nəl/. This means that it would start with the "b" sound, followed by "i" as in "eye", "g" as in "goose", "er" as in "herd", "m" as in "mother", "in" as in "pin", and "al" as in "pal". It's always important to double-check the spelling and pronunciation of unfamiliar words before using them!
Relating to two germs or ova.
A practical medical dictionary. By Stedman, Thomas Lathrop. Published 1920.