/ Dictionary / Index S senility: Meaning and Definition of Find definitions for: se•nil•i•ty Pronunciation: (si-nil'i-tē), [key] — n. the state of being senile, esp. the weakness or mental infirmity of old age. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: senility (Thesaurus) senile macular degeneration senior Related Content Daily Word Quiz: neologism Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language