Marked by neglectful or heedless failure to remember: forgetful of one's responsibilities. (adjective)
Causing one to be unable to remember.(adjective)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "forgetful" in a sentence
"The newest incentive fad is to pay the "forgetful" to take their medicine."
"Even in the fanciest of fancy Assisted Living Units -- like one I saw with slick silver salt shakers, state-of-the-art elevators and a door-alarm system disguised behind paneled walls, as well as a pristine health spa with fluffy white towels, reminiscent of five star hotels -- the "forgetful" are not allowed outside the bounds of their "ward", unless they ask permission."
"Old people vote so there will never be a mental competency test for doing open heart surgery because you'd scare everyone that being "forgetful" will deny you an operation."