I came up with a new term today - scope sneak.

Sneak [sneek]: verb, sneaked or snuck, sneak·ing, noun

–verb (used without object)

1. to go in a stealthy or furtive manner; slink; skulk.
2. to act in a furtive or underhand way.
3. British Informal. to tattle; inform.

Something happened at work today when a friend highlighted that some requirements had been snuck into a requirements document he was developing from. It occurred to me that this isn’t really scope creep (also seen here). Scope creep to me implies that everyone on the project knows that requirements are being added or changed (usually expanded). This situation was a bit more like requirements were added on the sly, hence scope sneak.