Here are some nuances:
* It's not always negative: While it can describe someone who's acting irrational or silly, it's often used playfully to describe someone who's quirky, passionate, or overly enthusiastic.
* Can be applied to situations: It can also describe a situation that's chaotic or absurd.
* Often used with humor: It's frequently used in a humorous way, even if the person being described is actually acting crazy.
Examples:
* "My grandma is such a meshugina; she always tells the same stories over and over."
* "It was a meshugina party; there was music blasting, people dancing on tables, and everyone was just having a blast."
* "You're being so meshugina! Don't worry about it so much."
Note: While the word itself is Yiddish, it's become somewhat popular in English as well, particularly in Jewish communities.