Suppress, repress both mean to hold back by the use of more or less force someone or something that seeks an outlet (as by expression or activity).
Suppress carries a strong implication of putting down or keeping back completely. It usually implies the exercise of great or oppressive power or even of violence. It often is a synonym of such words as overpower , crush , abolish , destroy , eliminate , or stifle , but in each case it tends strongly to suggest the prompt use of effective methods.
Repress, on the other hand, implies little more than a checking or restraining sometimes by an external force, sometimes by the power of the will or mind. It often suggests that the thing so held back may break out again or in a different way and so comes close to inhibit , bridle , or curb .
In psychology suppress is commonly used with reference to desires, instincts, and emotions which are consciously and forcibly inhibited by the mind from seeking expression or overt activity; repress usually suggests an unconscious or subconscious process by which a desire or an impulse that is regarded as unacceptable because of one’s religious, moral, or social training is inhibited by a refusal to recognize it or to permit consideration of it and so is left to operate in the unconscious.