noun

• (architecture) A fanciful building built for purely ornamental reasons.
  "A luncheonette in the shape of a coffee cup is particularly conspicuous, as is intended of an architectural duck or folly."

verb

• (dialectal) To follow.
  ""You got any money?" he said to me. ¶ "Hell no, maybe enough for a pint of whisky till I get to Denver. What about you?" ¶ "I know where I can get some." ¶ "Where?" "Anywhere. You can always folly a man down an alley, can't you?""

noun

• (largely obsolete outside place names) A clump of trees, particularly one on the crest of a hill (or sometimes on a stretch of open ground).
  "'Every hill seems to have a Folly' [...] 'I mean a clump of trees on the top.'"