Hi Eva! It depends on the sentence, but it can mean either "be cheating someone"/"be kidding someone" and "hesitate doing something". Literally, it means "go teetering/hesitating", but the first meaning is the most used one. I hope it could be useful

It has many meanins depending of the country(or zone) and situation.

"Andar vacilando por la calle" es una expresión informal, sería andar para que la gente te mire. it means to walk so that the people watch at you

it means something like this: when you say a lie to anoher person, and your objective is make a joke. Another meaning is when you have doubts