creepy, iffy, fairly unsafe, an air of uncertainty, not kosher, and just generally something or someone that you don't want to be associated with (or really do want to be associated with, depending on who you are...)
1. That guy staring at me is really sketchy.
2. This Waffle House is really sketchy.
3. I don't know if I like Steve's driving--it's kinda sketchy.
Prices shown in USD.