What does "sticker" mean?

Sticker: That which causes one to stick; that which puzzles or poses. [Colloq.] Tackeray.

Additional senses

  1. 2.(Mus.) In the organ, a small wooden rod which connects (in part) a key and a pallet, so as to communicate motion by pushing.
  2. 3.Same as Paster, 2. [Political Cant, U.S.]

Sources