What did conscientious objectives mean in World War 1?

Do you mean "conscientious objector"? A conscientious objector (or "CO") is a person whose conscience (his sense of right and wrong) does not allow him to fight for ANY reason.

It is sometimes difficult to determine if a person who refuses to go into the Army is really morally opposed to war or conflict in any form, or if he simply does not want to fight in THIS war, for THESE reasons. Or if he is genuinely a coward. Many COs were assigned to medical units; they would not be in combat themselves, but would serve as medics and orderlies assisting the doctors treating the wounded.