Although Wikipedia says there's no agreement on the definitions of "widow" and "orphan" (http://en.wikipedia.org/wiki/Widows_and_orphans), web research has led me to conclude that there's a stronger consensus than Wikipedia credits: that orphans are at page bottom and widows at page top. As two data points, these are the definitions used by typography expert Robert Bringhurst (as quoted long ago on this list by Steve Izma (http://lists.gnu.org/r/groff/2004-03/msg00091.html), himself a knowledgeable and experienced typographer), and are the ones assumed by the -ms parameter names PORPHANS and HORPHANS, which control bottom-of-page line allotment.
This part of commit 78b4d92c4, on the other hand, introduced text in the groff info manual a couple weeks ago using the opposite definitions: > +@cindex widow > +We can require space for at least the first two output lines of a > +paragraph, preventing its first line from being @slanted{widowed} at the > +page bottom. What do our resident typographers regard as a widow and an orphan?