Learned another interesting term, courtesy of fellow budoka/blogger Pat Parker (the definition comes from a handful of sources):
Shikaku: Literally, the "dead angle" or dead corner, or the vulnerable angle. Position relative to one's partner where it is difficult for them to continue to attack, and from which it is relatively easy to control one's partner's balance and movement. The first phase of an aikido technique is often to establish shikaku.
Pat, then, takes the term a bit further to refer to those place where uke can't quite see what tori is up to, such as with shomen ate. Well, just read how he explains it.
It's interesting to me how it might relate to judo as well. I haven't given it a lot of thought, so while I can't think of a specific example other than the fact that, when grappling with guys who know what they're doing, you very rarely see the choke or the arm bar coming. Hmmm....