What is the meaning of tower?

noun

• A structure taller than its diameter; can stand alone or be attached to a larger building.
• Anything that approximates the shape of a column or tower.
  • usage: "the test tube held a column of white powder"; "a tower of dust rose above the horizon"; "a thin pillar of smoke betrayed their campsite"
  • synonyms: column, pillar
• A powerful small boat designed to pull or push larger ships.
  • synonyms: tugboat, tug, towboat

verb

• Appear very large or occupy a commanding position.
  • usage: "The huge sculpture predominates over the fountain"; "Large shadows loomed on the canyon wall"
  • synonyms: loom, predominate, hulk