I found this on a site linked to the language of lagomorphs. I needed a break from my dissertation.
Tail Wag
Susan R. posted to the guestbook about a "lateral tail wag." She wrote,
I’ve seen several of my rabbits do this (a side to side move of a relaxed tail) as they hop away from another bun. This is usually after Bun #1 (the wagger) sniffs Bun #2. Sometimes a slight head binkie from Bun #1 is involved. From the expressions of the wagging buns, it seems that wagging may be similar to a "foot flick" or may be a sign of mild annoyance.
I’ve seen it a few times now in our own rabbits (addressed to me!) and I’m pretty sure she’s got the meaning exactly right. It’s a milder put down than the foot flick, but definitely seems to have a related meaning. It’s just amazing how one can totally miss some of these signals, but once you know to watch for them they become all but obvious.
Some folks on the alt.pets.rabbits newsgroup have reported that the tail wag is a happy signal. Reading Susan’s description of the circumstances above certainly can lend itself to that interpretation too, but I admit it didn’t appear that way the couple of times I’ve seen it. I think the closest human signal might be sticking your tongue out as a mild mocking gesture.
This one needs more study.