sticker in WordNet English dictionary

1. a short knife with a pointed blade used for piercing or stabbing
   dagger  sticker 
   
2. an adhesive label
   gummed label  sticker  paster 
   
3. a particularly difficult or baffling question or problem
   poser  stumper  toughie  sticker 
   
4. a small sharp-pointed tip resembling a spike on a stem or leaf
   spine  thorn  prickle  pricker  sticker  spikelet