Repression is a decrease in the rate of synthesis of an enzyme specifically caused by a small molecule which is usually the end product of a biosynthetic pathway, e.g., an amino acid or nucleotide.
Definition in Social Psychology
Repression is a defensive response to threat in which the person attempts to control anxiety by using avoidance mechanisms such as denial and forgetting.
In psychoanalysis, repression is a defense mechanism and a crucial concept in Freudian theory. The essence of repression is the blotting out from conscious awareness of disturbing feelings and impulses arising from the ID. They are submerged in the unconscious-where they invariably get up to mischief.