Dissemble means "to conceal," "to give a false appearance," "to feign": "Try to dissemble your lack of interest by looking alert." "Roy dissembled his guilt by grinning broadly." Dissemble is a synonym of dissimulate. Disassemble means "to take apart": "He disassembled the motor and then found he could not put it together again." Disassemble is the antonym of assemble.
Dictionary of problem words and expressions. Harry Shaw. 1975.