But that leak to the Washington Post was a sign, I suppose, that they're going to put some serous political capital into this.
early 15c., "watery," later "of or pertaining to serum" (16c.), from French séreux (16c.) and directly from Latin serosus, from serum "watery fluid, whey" (see serum). Related: Serosity.
serous se·rous (sēr'əs)adj. Containing, secreting, or resembling serum.