Someone who acts suspicious, unpredictable and odd in normal situations. Someone who lacks common sense and is overly secretive. Usually someone who has used a high volume of Valium.

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

Lacking integrity
Dishonest
Untrustworthy

Corrupt
Jesse May

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...)

Iffy. Questionable.

Something that doesn't seem right, or you're unsure of, or that is just kind of not in your comfort zone.

This expression was first coined in reference to hastily drawn out, or sketched, building/construction plans, which were uncertain at best and disastrous at worst. The overall thread of meaning is the same, but now applies to morality/legality. On the overall continuim of goodness, things progress, in order: safe, sketchy, shady, outright criminal.