1. Unpredictable (closest to mathematical definition); weird. "The system's been behaving pretty randomly."
2. Assorted; undistinguished. "Who was at the conference?" "Just a bunch of random business types."
3. (pejorative) Frivolous; unproductive; undirected. "He's just a random loser."
4. Incoherent or inelegant; poorly chosen; not well organised. "The program has a random set of misfeatures." "That's a random name for that function." "Well, all the names were chosen pretty randomly."
5. In no particular order, though deterministic. "The I/O channels are in a pool, and when a file is opened one is chosen randomly."
6. Arbitrary. "It generates a random name for the scratch file."
7. Gratuitously wrong, i.e. poorly done and for no good apparent reason. For example, a program that handles file name defaulting in a particularly useless way, or an assembler routine that could easily have been coded using only three registers, but redundantly uses seven for values with non-overlapping lifetimes, so that no one else can invoke it without first saving four extra registers. What randomness!
8. A random hacker; used particularly of high-school students who soak up computer time and generally get in the way.
9. Anyone who is not a hacker (or, sometimes, anyone not known to the hacker speaking). "I went to the talk, but the audience was full of randoms asking bogus questions".