Operating or functioning in an impaired or abnormal way.
Example:
His sisters constantly claimed that the family was dysfunctional, but he could never see it.
Neurologists speak of dysfunctional brain stems, and psychiatrists treat patients for dysfunctional sexual response. Political scientists wonder if the American two-party system has become dysfunctional, and sociologists point to the rising crime rate as evidence of a dysfunctional society. Nowadays dysfunctional more often describes families than anything else. In popular usage, any family with problems is likely to be characterized as dysfunctional.