Mime

MIME

-noun
1. the theatrical technique of expressing an idea or mood or portraying a character entirely by gesture and bodily movement without the use of words
2. a performer specializing in such a technique
3. a dramatic presentation using such a technique
4. (in the classical theatre)
a. a comic performance depending for effect largely on exaggerated gesture and physical action
b. an actor in such a performance
-verb
5. to express (an idea) in actions or gestures without speech
6. (of singers or musicians) to perform as if singing (a song) or playing (a piece of music) that is actually pre-recorded

In the face of strangers

They mime their knowledge

Or resort to crude Latin

In an attempt at Esperanto