poser

Short definition from Wiktionary

Noun

1. 1
   A particularly difficult question or puzzle.
2. 2
   Someone who asks a question or sets a problem.
3. 3
   Someone who, or something which, poses; a person who sets their body in a fixed position, such as for photography or painting.
4. 4
   A poseur; someone who affects some behaviour, style, attitude or other condition, often to impress or influence others.

Proper noun

1. 1
   A surname from German