Women's Institute

From Tardis Wiki, the free Doctor Who reference

A WI was a local organisation of women who came together to enjoy special activities, food and fellowship. Joan Redfern's Farringham-area WI once met to hear a lecture by Alexander Shuttleworth on the archaeology of bronze age Britain.

Beyond the academic discussions, the WI meetings were also naturally a haven for gossip. Redfern herself was the subject of some gossip from time to time. (DWM: Prelude Human Nature)

WI stands for Women's Institute — a real-life British organisation. The acronym is never explained, however, in either Human Nature or its prelude.
Women's Institute