The definition of idiosyncratic is quirky or peculiar, or the temperament which is unique to an individual. (adjective)
- An example of an idiosyncratic person is someone who does a lot of out of the ordinary things.
- An example of an idiosyncratic trait is the way a person always deals with disappointment.
- An example of an idiosyncratic reaction to a drug is the unique way that someone reacts to a medication.