Spaz
The meaning of this word differs depending on which country you're in.
If you're in the USA, it's used to describe clumsy people. However, if you're in the UK, it's a slur towards disabled people (particularly ones with cerebral palsy). So, be careful and take note, that if you're American, to not use that word around Brits.
USA
A kid shouts out in a class: "LOL! Tim is such a spaz!"
"Thank you for that John. Now, can I continue with my lesson?"
UK
The british kid shouts out in a class: "LOL! Tim is such a spaz!" (gets b-slapped by a teacher)