UK:*UK and possibly other pronunciationsUK and possibly other pronunciations/ˈkɒstli/US:USA pronunciation: IPA and respellingUSA pronuncation: IPA/ˈkɔstli, ˈkɑst-/ ,USA pronunciation: respelling(kôstlē, kost-)

Inflections of 'costly' (adjadjective: Describes a noun or pronoun--for example, "a tall girl," "an interesting book," "a big house."):
adj comparative
adj superlative

WordReference Random House Learner's Dictionary of American English © 2020
cost•ly /ˈkɔstli, ˈkɑst-/USA pronunciation   adj.,  -li•er, -li•est. 
  1. costing much;
    high in price:a costly mink coat.
  2. resulting in great loss:a costly mistake.
cost•li•ness, n. [uncountable]

WordReference Random House Unabridged Dictionary of American English © 2020
cost•ly  (kôstlē, kost-),USA pronunciation adj.,  -li•er, -li•est. 
  1. costing much;
    high in price:a costly emerald bracelet; costly medical care.
  2. resulting in great expense:The upkeep of such a large house is costly.
  3. resulting in great detriment:It was a costly mistake because no one ever trusted him again.
  4. of great value;
    very valuable;
  5. lavish;
costli•ness, n. 
  • Middle English costli. See cost1, -ly 1350–1400
    • 1.See corresponding entry in Unabridged dear, high-priced. See  expensive. 

Collins Concise English Dictionary © HarperCollins Publishers::
costly /ˈkɒstlɪ/ adj ( -lier, -liest)
  1. of great price or value; expensive
  2. entailing great loss or sacrifice: a costly victory
  3. splendid; lavish

ˈcostliness n
'costly' also found in these entries:

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