This is the errno for "No space left on device". Predominantly, the error occurs if trying to write onto a full filesystem. To confound things, the System V IPC APIs (and, consequently, more new interfaces) treat object spaces like disks/filesystems, possibly returning this error, too. This shouldn't be a problem, but like many others, the short description is suboptimal: it should really be just "No space left".

The common pitfall of errno codes: they weren't made truly general.