siˈsternityrare. [f. sister n., on the analogy of fraternity.] Sisterhood. 1603Harsnet Pop. Impost. xxiii. 166 A Sisternity of mimpes, mops, and idle holy women.1654Gayton Pleas. Notes iv. ix. 235 Others of their sisternity (very weak headed women, frail vessels) carried not matters so well.