verb

• (transitive) To be higher than; to rise over the top of.
  "From thence we came without the Eaſtern gate, (ſtanding on a low Banke, called the daughter of Syon, that over-toppeth the valley of Iehoſaphat,) unto an immoveable ſtone, upon the which they ſaid St. Stephen was ſtoned to death, the firſt Martyr of the Chriſtian faith; and the faithfull fore-runner of many noble followers."
• (transitive) To place too many toppings on.
  "to overtop a pizza"

adv

• (now chiefly Canada, US) Over the top.
  "Paul put the skull back in its proper place, put back the coffin lid, and kicked dirt and rocks overtop."

noun

• (clothing) A garment designed to be worn over the top portion of other clothes, such as an overshirt, vest, or overtunic.
  "Featured is the big plaid, streaked with white in a softly gathered skirt & an overtop of velveteen with a dacron polytester^([sic]) oliver bow blouse in white."