n. Lack of capacity; lack of ability or qualification; inability; incapability; incompetency.n. In law, the lack of legal qualification; that condition of a person which forbids a given act on his part, and makes the act legally inefficacious even if he does it: as, infancy constitutes an incapacity to contract; a trust creates in the trustee an incapacity to buy the trust property for himself at his own sale.