Dysphoria is the opposite of euphoria (a state of happiness). It is generally characterized as a feeling of emotional and/or mental discomfort, restlessness, malaise, and depression.
A person suffering from dysphoria will feel that "Things aren't the way they are supposed to be."
One type of dysphoria is gender dysphoria; people who suffer from this disorder feel uncomfortable with their identity in the gender/sex they have been assigned.
Chronic dysphoric mood states may also be a contributing factor in the development of eating disorders, depression, and sometimes drug and alcohol abuse. Dysphoria can be differentiated from depression in that it tends to be an agitated feeling. That is, dysphoria is often described by sufferers as a "bad high" as opposed to the "low" of depression. Sufferers of bipolar disorder often suffer from dysphoric highs, making the stereotype of "bad when low, great when up" bitterly ironic.