1. (of a program) Badly written.
2. Functionally poor, e.g., a program that is very difficult to use because of gratuitously poor (random?) design decisions. Oppose cuspy.
3. Anything that manipulates a shared resource without regard for its other users in such a way as to cause a (non-fatal) problem. Examples: programs that change tty modes without resetting them on exit, or windowing programs that keep forcing themselves to the top of the window stack.