Definitions of tick:

• noun:   any of two families of small parasitic arachnids with barbed proboscis; feed on blood of warm-blooded animals
• noun:   a light mattress
• noun:   a metallic tapping sound

  Example: "He counted the ticks of the clock"

• noun:   a mark indicating that something has been noted or completed etc.
• verb:   make a sound like a clock or a timer

  Example: "The clocks were ticking"

• verb:   sew

  Example: "Tick a mattress"

• verb:   make a clicking or ticking sound

  Example: "The clock ticked away"

• verb:   put a check mark on or next to

  Example: "Tick off the items"

• name:  A surname (very rare: popularity rank in the U.S.: #59698)