Bism is used in conversations between lovers, when one party is already involved with someone else. It is used when one party is trying to be "sensible" and not let themselves fall deeper into difficult, emotional, situations.
Follow your heart, jump in your car and come and move in with me. We are meant to be. Stop being bism!
A bism is a term for someone who is deliberately irritating or annoying, but a less harsh term than 'bitch' when that is deemed inappropriate.
'Stop pestering me with your ridiculous questions, you silly bism!'
The piece of flesh between a woman's vagina and her anus.
I'm sure I was told this meaning when I was in the army in 1985 - have used it ever since.
You shaved your muff
but not your bism.