sticker

noun

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