se ‧ nile /ˈsiːnaɪl/ BrE AmE adjective
[ Date: 1600-1700 ; Language: Latin ; Origin: senilis , from senex ; ⇨ ↑ senior 1 ]
mentally confused or behaving strangely, because of old age:
a senile old man
She worries about going senile.
—senility /sɪˈnɪləti, sɪˈnɪlɪti/ noun [uncountable]