If old people become senile, they become confused, can no longer remember things, and are unable to look after themselves. + senility se·nil·ity The old man was showing unmistakable signs of senility. mentally confused or behaving strangely, because of old age (senilis, from senex; SENIOR)
{s} pertaining to old age, geriatric; suffering from physical and/or mental impairments associated with old age