Some definitions of "Sketchy"

From the Merriam-Webster Dictionary:

Inflected Form(s): sketch·i·er; -est
1 : of the nature of a sketch : roughly outlined
2 : wanting in completeness, clearness, or substance: slight, superficial <the details are sketchy>
3 : questionable, iffy <got into a sketchy situation> <a sketchy character>

From Berkeley's Online Slang Dictionary:

sketchy adj 1. suspicious. ("That deal sounds rather sketchy.") 2. dangerous. ("That's a pretty sketchy part of town.") 3. of questionable character, strange. ("I'd stay away from that guy, he looks sketchy.")

From www.slangsite.com:

sketchy: Unsettling or questionable.
Example: Check out that sketchy guy--no, not him! The one with the chainsaw, doofus.

From Peak English Online English School's Slang Dictionary:

SKETCHY: Suspicious or shifty; causing some anxiety or unease.

From UrbanDictionary.com:

1. Sketchy

1) someone or something that just isnt right.
2) the feeling you get the morning after using a lot of drugs, most commonly associated with ecstacy.
3) something unsafe
4) someone or something that gives off a bad feeling

i dunno, his story sounds kind of sketchy

2. Sketchy

Iffy. Questionable.

That huck was pretty sketchy