expensive-The definition given to you was "costly, high-priced." Other synonyms could have been provided because English is quite rich in that area. Webster's Dictionary of Synonyms, for example, contains ten entries that explain expensive or show us slight variations of the word: costly, dear, valuable, precious, invaluable, priceless, exorbitant, excessive, immoderate. When would you use costly as a synonym for expensive and when would you use excessive?