Un-burden refers to the act of relieving oneself from stress or burden. Antonyms for the word un-burden are related to adding burden or stress to an individual. These words are heavy, weigh down, burden, load, lumber and saddle. Heavy refers to something that is difficult to carry and is a burden that causes stress. Weigh down means to add extra weight or pressure to a person or situation. Burden is a noun that refers to a sense of duty or responsibility that adds stress. Load means to add or place heavy objects that cause difficulty in carrying. Lumber and saddle both refer to carrying a heavy load in a clumsy, awkward and burdensome way.