
| 1. | a characteristic, habit, mannerism, or the like, that is peculiar to an individual. |
| 2. | the physical constitution peculiar to an individual. |
| 3. | a peculiarity of the physical or the mental constitution, esp. susceptibility toward drugs, food, etc. Compare allergy (def. 1). |

idiosyncrasy id·i·o·syn·cra·sy (ĭd'ē-ō-sĭng'krə-sē)
n.
A structural or behavioral trait peculiar to an individual or a group.
A physiological or temperamental peculiarity.
An unusual individual reaction to food or a drug.