Stack overflow is what happens when you try to push an item onto a full stack, and the stack does not detect the stack-full condition (or handles it catastrophically, with a page fault or similar processor exception, or by clobbering other data). This is bad. In a security context, a StackOverflow is a case of BufferOverflow that occurs on the stack, as opposed to the heap. StackSmashing is when crackers purposely try to overflow a stack to overwrite data in and beyond the current stack frame. Usually, they will overwrite the return address at the end of the frame, and then place ShellCode? beyond that address in hopes of executing arbitrary code. This is really bad.
Can refer to any data structure (of bounded size) used to represent a stack. Often, the stack being referred to is... TheStack.
I tend to browse through this Wiki, jumping from interesting link to interesting link, until I hit StackOverflow in my head. Then I close my browser.
StackOverflow is also the name of a programmers' QuestionAndAnswerWebsite? developed by JeffAtwood and JoelSpolsky. http://stackoverflow.com/