From Battlestar Wiki, the free, open content Battlestar Galactica encyclopedia and episode guide

Sire is a Colonial title used to denote males of some important stature.

For example, all male members of the Quorum of Twelve had the title of Sire, such as Sire Uri or Sire Domra.

"Sire" is similar to the use of the title "Sir" as an honorific of British knighthood. Only British subjects can use the "Sir" article, such as author Sir Arthur Conan Doyle, or actor Sir Sean Connery.

The female equivalent of the honorary title of Sire is "Siress."