A person, place, or event that is of questionable quality and/or reputation

someone extremely sketchy

1. One who is "sketch" quite often.

This activity occurs when you are in public and you see a police officer. The game goes as followed.
1. Spot a police officer or someone in law enforcement.
2. Look at him/her and make sure he/she sees you clearly.
3. Run as fast as you can in the opposite direction.
4. Results may vary.

Someone who in the presence of other people makes them feel uncomfortable or weirded out. In some cases such acts will result in the "non-sketchball" to physically or verbally abuse the sketchball"

a sketchy kid, someone who is sketchy beyond belief, a stalker

A term used in an incredibly already sketch situation, adding more dramatic effect towards the word sketch.