When you have to hide your boner, you're Incocknito.
I had to go Incocknito at the pool party yesterday.
The art of having a sly wank unnoticed by the surrounding public, ideally practised on public transport, shopping malls or places of authority. Aimed at the gender/animal of your choice.
Mummy why has that person gone red in the face? Ignore him Beatrice, I think he's incocknito