How do you define common sense?

Common sense to me is something that is very obvious to you...
For example: Hungry, then you eat. You see someone cry, move away or console them (depending on how well you know the person). See someone angry, first thing you do is avoid their wrath until they calm down. Stuff like that.
Common sense is something built inside a person, when you need to use it, it's there.
Unfortunately, not everyone holds the same concept to common sense.
My mum for example.
"You going to overnight at your aunt's place tonight with us, right?"
"No, I'm already out and didn't pack my clothes. Why would I know to pack clothes?"
"It's common sense that if your parents are here, you pack your clothes and overnight with them."
And listen to old aunties gossip the whole night and telling me what to do with my life?
Common sense tells me to stay as far away from them as I can.