Run Rampant Meaning

(idiomatic) To go unchecked or without control; to be wild or excessive.

Example: The weeds had long run rampant in the garden and it would be difficult to regain control.
2012 March 1, William E. Carter, Merri Sue Carter, “The British Longitude Act Reconsidered”[1], American Scientist, volume 100, number 2, page 87:
  Conditions were horrendous aboard most British naval vessels at the time. Scurvy and other diseases ran rampant, killing more seamen each year than all other causes combined, including combat.