covertpen
nounUK /ˈkʌvət pɛn/
US /ˈkoʊvərt pɛn/
A pen that is made to look like something else so people do not notice it.
The spy wrote a secret note with a covertpen that looked just like a normal marker.
OTHER MEANINGS
2. A small hidden enclosure for animals, such as a secret pen for sheep.
The farmer kept the sick lamb in a covertpen behind the barn.
3. A quiet, sheltered place where someone writes privately.
She turned the attic into a covertpen for her diary and stories.
4. A pen used to write in invisible or coded ink.
He used a covertpen to leave a message only his friend could read.