Mu

1). Being passive aggressive or quite during a confrontation. then afterwards you lash out on others that supports/ loves you.

2) Lashing out on a friend or loved one after the fact for a perceived slight when in fact you're the one in the wrong.

1. Bro, I'm sorry she knew Spanish better then you, but your mu response by lashing out at her is very childish.
2. When I was chatting up a hottie next to her BF, he sat silently. Later he went "mu" and yelled at her for not respecting his boundaries.