Definitions of bristle:

• noun:   a stiff hair
• noun:   a stiff fiber (coarse hair or filament); natural or synthetic
• verb:   rise up as in fear

  Example: "The dog's fur bristled"

• verb:   be in a state of movement or action

  Example: "The garden bristled with toddlers"

• name:  A surname (very rare: popularity rank in the U.S.: #38495)