From The Poly Dictionary, a definition I thought was worth quoting.
LESBIAN SHEEPITUDE: Colloquial A term used to describe a situation where one person has a romantic or sexual interest in another person, which may be reciprocated, but neither of them indicates this interest or makes the first move. Etymology: The colloquialism comes from the behavior of sheep; a female ewe indicates sexual interest and receptiveness by standing still, so two hypothetical lesbian sheep would indicate their sexual receptivity by each standing still, and no mating would take place. Commentary: This expression is often heard on the UseNet newsgroup alt.polyamory.
This is a great term for a phenomenon that I've experienced all too frequently (and I'm sure most of you have as well), despite being neither lesbian nor ovine. I think I'll start using it. If nothing else, "sheepitude" is almost as fun to say as "Latvia"!